On my previous 94 Grand Prix SE 3.1L at 165,000 miles, my head gasket blew and the head cracked in half. Other than that, just regular maintenance, (brake pads, Disc and exhaust.) The 94 ran for over 240,00 miles before I let my son have it, so he could trade it in for a 2004. It still ran like a top.
On my present 98 Grand Prix GTP, at 131,000, I am getting ready to replace my SC nose drive, instead of rebuilding it. The nylon type bushing was wearing, and I let it go too long, and now it is affecting my bearings. You can replace the bushing yourself, but to do the bearings, you need a Hydraulic press. I feel it is cheaper to go to ZZperformance.com and buy a completely rebuilt nose for $200 with better than OEM parts. If you plan to put a smaller pulley on, buy it from them and they'll install it for free when you buy the nose. Also, their bushing is of better material than that of the OEM one, and will last way longer.