I'll provide my feedback embedded in your note below. You have already received excellent advice, but I'll pile on with what I know.
Of the advice you have gotten, start small is great advice until you know where you want to go. A 60 foot long layout is a HUGE endeavor.
I would also recommend that you stay with 30" wide benchwork maximum as much as possible, and if you are going to have visitors, or do operations with a group, keep your aisle with to 3 foot minimum. This is not always possible.
Use backdrops to get the illusion of depth, instead of modeling distant mountains in 8 foot depth scenes. Waste of space IMHO.
so ive been at the point where im pretty much finished with benchwork on a pretty sizable basement layout originally planned for O scale. the past few days I have been seriously considering going the HO route instead. I have so far amassed a good amount of gargraves track and turnouts which none have been installed yet (some wire leads , but no other electrical equipment yet), so I figure now is the time to decide. my firs model RR experience back in elementary / middle school was a 4 x 8 HO , my friends back then had early lionel / tube track sets which really did nothing for me.. I guess I was attracted more towards the realism aspect. only in adulthood I have been turned on to the O scale and have been learning all I can at a furious pace in the past months. however , now that I have been learning more about todays HO and comparing what I want to do vs cost / availability etc etc, this has me about to switch sides. forgetting all the pitfalls of early HO , I want to field some questions to the forum for your expertise.
- what is the difference between the track "codes" ? what is the more popular / best to go with?
As stated by others, the "Code" is the rail height in thousanths of an inch. So, code 83 is 0.083" high. This is the size that I use.
There is nothing wrong with Code 100 either (0.100" high), but the Code 83 looks better.
Another popular track size is Code 70. Some people model the following:
Code 83 for the main line
Code 70 for passing sidings
Code 55 (which they hand lay) on sidings, and industrial trackage.
Looks great. I stick with code 83 for everything. Once it is weathered, in my opinion, it looks fine. My commercial track of choice is Peco. I am also using Walthers Shinohara switches. I wish I went with Peco instead. I really like the look of Peco switches, and their quality is second to none. So far, I am impressed with the Shinohara DCC friendly switches, but I don't know how they will perform over the long term.
- what turnouts are considered DCC friendly and ready to install?
The three switch manufacturers that I would choose from are Atlas, Peco, and Shinohara (they are the only ones I have experience with, other than Micro Engineering, and I HATE their switches). All three offer DCC friendly switches, the Peco "Insulfrog" would be my choice, with the frog powered thru auxilary contacts on your switch machine, which you would do on the other two.
- I would plan on actuating switches locally via the remote switch as opposed to through a remote control , so is track power acceptable to run turnouts in the HO world?
Under the scheme that you are discussing, I would route a separate 12 VDC bus with it's own power supply to control the switches, thru a DPDT toggle switch. Use Tortoise or SwitchMaster switch machines (SwitchMaster machines require you to add the separate aux contacts, which is a bit of a PITA).
- what is the best command control system to use with HO these days
DCC is the way to go. I utilize NCE DCC, and for a layout the size you are looking at, you want to utilize the 5 amp power supply. You may need more than one power booster, and you should break your bus wiring into districts, and utilize electronic circuit breakers for each district.
I've run layouts with NCE, Digitrax, and MRC, and they are all great systems. No experience with Atlas, Lenz, or Easy DCC.
- what wiring technique is used (star wiring etc etc) is it similar to O gauge DCS?
You do NOT need to star wire DCC. I have a basement sized HO railroad, what I do is the following:
10 gauge wire from the power booster out to my powershield circuit breakers, which are in close proximity to the layout (probably overkill, but I had the 10 gauge wire).
14 gauge bus wiring along your power districts.
I utilize 16 gauge to the track, but I LIKE good strong solder joints. Once the track is weathered, the size of my track feeder attachments are not noticeable. You could get by with 18 to 20 gauge on the feeders.
I also utilize 3M insulation displacement connectors for the bus to feeder wiring. I will NEVER solder a feeder connection to a bus wire ever again.
- what kind of power do I need to run a layout that would be approx. 60' long / 4 to 8 ft deep depending on area.
The 60 feet long is a great plan. The 4 to 8 feet deep is in my opinion a mistake. I am a big believer in "shelf" style layouts, and the deepest portion on my layout, with the exception being the ends of my shelves where the 36" plus radius is located is 30" deep. That is far as the average human can reach without standing and leaning over the layout.
I HATE duckunders, and crawling on floors to get access to hatches within the layout, but then again, based on your career, I think you are in far better shape than I am. 
- using flextrack , what is the best method for cutting the rails?
I prefer using a cut-off wheel in my Dremel. I've used rail nippers (Xuron), and they work fine too. Try both, determine what works best for you.
- what exactly is the difference between a "DCC ready" / DCC / PS2/3 locomotive and the benefits of either? can an MTH proto loco be used on other DCC systems etc etc?
DCC ready means there is a plug wired into the locomotive that you would install a DCC decoder into with the similar plug. These are typically non-sound locomotives. Atlas "Silver" locos fall into this category.
DCC equipped locomotives may be just motor and light control, or most today are motor / light / sound decoders. Atlas "Gold" locomotives fall into this category.
MTH PS3 decoders are roughly equivalent to a DCC equipped sound / light / smoke / and motor control decoder. I don't own any MTH HO product, so I cannot say how good they work. I've seen them in operation, and they work in DCC mode just like most other locomotives, with the only limitations being in programming CVs (at least on their earlier releases). I'm considering purchasing two of their upcoming DM&IR M-4 Yellowstones, saw them at Portland, looked good, good price.
I know its many questions , but depending on the answers will most likely sway me.
thanks guys!
