On my first PS3 upgrade (steam) I had the same thing where there was a sound set loaded already in the boards from the factory. It was also a diesel sound set. The thing was the sounds were so clear and real sounding (especially the bell) I was kind of bummed that I had to erase them but just in case I needed them again someday I first copied them to my computer.
I dodged a real bullet on this one. What happened was: First I copied the program to my computer. That took 2 hours. I then tried to load the new files. I had a lot of trouble as I kept getting errors and the MTH Loader Program kept locking up. Finally, I thought it has to be something with my computer. I then decided to disconnect the Wi-Fi and turn off any programs that might be running in the background and might be interfering with the MTH Loader Program. All regular applications were already off but now I shut down everything that has to do with my Anti-virus software. I still had a few errors but the software loaded. The problem was when I copied the original software to my computer the MTH Loader program gave me an estimate of 2 hours and it took about 1 hour and 55 minutes. When I went to load the new software to the locomotive I got an estimate of something like 20 minutes. I had to pick up my wife from the car repair shop she goes to 2 hours later so I thought I had plenty of time. Nope, 2 hours later it was still going but almost done. I couldn't keep her waiting so I left. I had the switch for the smoke off. I came back about another 2 hours later and the software had loaded properly but when it was completed the locomotive turned the smoke unit on. This smoke unit hadn't been run in like 12 years. It had no fluid in it. I then surmised that the smoke on/off switch doesn't turn on the power to the smoke unit. It tells the electronics that the user wants the smoke unit on and the electronics turn on the smoke unit. Or at least this is my guess. If I am wrong please correct me. Anyway, I got real lucky that I didn't ruin the electronics. However, after that the smoke unit was making a real loud squeaky noise like the bearing in it wore out or needed grease. It sounded just like an old HO AF/X car that needed oil. I was going to fix it right away but then decided to wait and see. So far the noise has been getting quieter so I am hoping that one day it will go away entirely. If not I will replace it then.
Lesson learned. If you have to leave the room while downloading the software to the locomotive make sure the smoke unit is disconnected!