K-Line 4-6-2 only runs reverse

I suspect your analysis is correct as far as the missing transistor.  One has to wonder if one or more of the other drive transistors is also bad.  Since TIP122 and TIP127 transistors are less than a buck each, I'd probably be inclined to replace all of them to start.

As far as documentation, finding detailed documentation on K-Line stuff is problematic to say the least.  OTOH, there's a lot of experience on these boards, and if you post pictures of the board, I'm sure one of us can help you get it running.  At the worst, replacing that board with a $15-20 reverse unit can be done if you can't get that one running.

Detailed pictures with the shell off would be useful.  The connection to the tender may be for the whistle, does the tender have center rollers?

The loco is a starter set type 4-6-2, and the drive wheels are not supposed to turn freely, except when under power. Many other modern era locos are like this as well.

The connector on the back of the loco is for an electronic upgrade. If you have an air whistle tender, the connector does nothing for you.

The switch on the bottom is either for the smoke unit or the reverse unit. I can't remember. Try it in each position to see if the smoke shuts off or if the trains runs in both directions.

Yes the switch is for the smoker, the drive wheels were so tight that they would not roll when the power was put to the train, they were rubbing on the chassis so I moved them out until they did not contact the chassis and it would run in reverse. I also had to synchronize them correctly. It now goes reverse like a mad man!!!

also it will need the drive roller traction bands.

Beware of buying trains on E Bay!

Didn't get this one off e-bay, got it local because it is cool. I didn't have to pay much so a repair won't be too bad. I have pics of the board but I am not sure how to post them.

Is it all running now?

Runs great in reverse, I ordered replacement transistors to try on it they should be here in couple days. Hope that's all it is.  I had someone tell me that the traction tires from a Lionel or MTH would work on this, is this true??

Yep, you just have to find the right ones.  FWIW, the correct tires will probably look to be too small in diameter, they do need to be stretched to fit in order to stay on longer.  If they're almost as large as the wheel, they usually will peel off pretty quickly when you have any strain on them.