I recently installed a DC Sports 4-1 ceramic-coated one piece into my 94 GSR. It was tricky because the one piece is a tight fit especially pushing up past the driver's side fan. I did not have to replace the o2 sensor (it is located post-header in my car). I did have the same problem as drive4show with connecting the lower portion (header to cat (especially with the new gasket) and lower hanger hardware) but there was no way to loosely attach both ends. This was frustrating, but a bit of muscle and some patience paid off. I had no problems with the head studs because I recently replaced all of them (yep I had an exhaust leak at the head a while back). I'll admit it was a tedious, but informative 3 hours. Probably seemed worse because I had to work on it in the hot sun. Wear safety glasses or be ready to blink fast while on your back. If it's a tie between diy or having it installed, I'd say get in there and learn about your whip! Find some shade, get a creeper and a torque wrench, and good luck.