As a point of interest, if the passenger seat either works fine or not at all(when you hit the switch it works great or not at all), then it is the switch. They sell for about $45 for my SD w/out memory, might be more for this car, so figure double at $90(probably way high). You do have to remove the door pannel to fix it though. Also, you can probably find a used wood piece(if you can't, i can give you a number which has them used and will ship) for around $90. As far as the rear window regulator, if your lucky it might only be a $12 dollar slide peice, but it sounds more serious. That could be the most expensive fix, if you actually want to fix it. I hear leatherique makes a great recondition system for leather that you describe, and i beleive can be had for around $65 for the cleaner/conditioner package, and has been said to work miracles(no first hand experiance yet, i want to try it though). All of the problems seem very minor to me, and easy to fix. Sorry i can't help on the engine, but i have read before the bottom ends are very strong, but at that mileage it could be due for a valve job(going off of what i've read on this forum). All the existing problems seem like minor annoyances to me.
R

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83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.