Tough question. Alot depends on how the previous owner took care of it. As long as you dont have the 2.7 and its problems, I would say 3.2 and 3.5 are very reliable engines. The 3.2 I bought and rebuilt for my car came out of a wreck with 211,000 miles on it. Common repairs from my experience, timing belt, crankshaft sensor, a/c & alt idler pulleys, oil pan gaskets, PCV hoses/valve, spark plugs & coil boots. My guess is that you will fix all of these once in 150,000 miles. There are a couple TSBs out on some of the older engines, 98-01 about ticking lifters and weak valve springs too.
The transmissions, they are very solid, again as long as there is good maintenance. The only problems here really are the input/output sensors and trans cooler line leaks.
As for the rest of the car, get ready to change the lower ball joints and stabilizer bar links. Also the clips that hold the window glass to the track tend to break.
Thats all I can think of for now, and 2gs are great cars and I would never give mine up. :biggrin: