'94 854 GTAS - 1st question: What is the difference between the 850 and the 854? And what does GTAS stand for? (GT = grand touring, I believe - but the rest I don't know)

2nd question: Sunroof makes noise when sliding back to full open position, and moves very very slowly, then stops when about 5" open. Won't budge, and can't get it closed unless I play with it back and forth, and finally have to slide the sun shield forward so it aligns with the open edge of the sunroof, and then it will close. Also noticed the roof is being pushed down by something on the driver's side - looking straight at it from the front of the vehicle, you can see how it dips down on the driver's side, as though something is pushing on it from the inside - could it be one of the plastic rails I've heard about that become detached and block the roof? Or is the fact that it makes a noise and moves so slowly indicating a dying motor? Suggestions? Note: opening the roof to "vent" position (up as opposed to sliding back) works fine.

3rd question: My car has 139,500 on it. I just had the timing and auxilliary belts replaced. But I'm wondering if there are other things I need to have done. Dealer says timing and aux. belt replacement are the only things at 140K. I've been reading posts that say the tensioners have to be replaced as well, and I didn't have this done nor was it suggested to me. I don't want to be surprised in the near future with yet something else and have already put a sizable amount of money into major repairs all in the last year: tranny flush, PNP switch, thermostat, ball joint, rotors/pads. Oil changed regularly every 3K miles.

Thanks for any advice and/or suggestions.