I have a 2001 IS, I got it at Lexus of Richmond in VA. I bought it new, its nice. You will enjoy it thouroughly. Mine is the Spectra Blue with black leather escain. I have the stock 17s, with new Sumitomo HTR Ultra High performance. I paid a little much for mine too, got a little hosed, but the car is hella cool, and very fast. As far as you getting hosed, maybe a little. But, you always feel like you are hosed after you leave a dealership.
Recently put a rod millen exhaust on, did not want the buzzer type exhausts you hear on these civics. I also have a AEM short ram intake. It sounds cool as hell, like a race car with just those two mods.
Stop by IS300.net, or Lextasy.com. They have a lot of parts, and the prices are not bad.
My future plans for mine is to redo my Speaker box, it takes up too much room in my trunk. I have 2 12 inch JL audio subs in a box. Along with a punch 360 amp. Nice deal, only 200 bucks. Just not enough room in trunk. Windows tinted, thats it right now. I want to get the TRD style rear spoiler, because at 100 mph, the back end feels a little light. I also have the JDM shortened chrome antenna on the roof, and diamond clear front side marker lights. not installed yet though. :o
Like I said before you will definetly enjoy, but you might want to upgrade the wheels to the 17 inchers for the better cornering.