Well, I just did this and it wasn't too bad. Getting the old O-ring turned out to be more difficult than I expected as it was basically a rock. I used a small flat-head screwdriver to slip it out. Was that wrong? Also, Shawn, I can't remember if you have UR pulleys? If so, check here for the timing marks:
http://www.sr20-forum.com/general-sr20/30154-ur-crank-pulley-timing-marks-question.html
If you have a Gspec pulley then check with Greg on the marks before you start this. It took me about half an hour to finish this project as I fumbled my way around but I think I got it. I got the $30 timing light from Harbor Freight (second cheapest) as the cheapest one got horrible reviews for not having a bright enough light to use at any time but at midnight during a new moon.