You'll find a pic of the IAC valve location on the site in the "Common problems-Driveability" section. It's not too hard to replace. Unplug the wiring, and remove the two bolts, top and bottom, although it's a bit of a reach to get at them.
If you look at the replacement part, it'll be obvious how it comes off. Took me about 10 or 15 minutes, and I'm an idiot, mechanically-speaking. The part cost me about $130 (Canadian), and the gasket was another 50 cents or so. (By the way, the article on the site says they are 8mm bolts. They're bigger than that, but I can't remember exactly. You'll soon find the right socket.)
I have been having a similar problem with my 99 SVT: rough idle, idling low - around 650-700 instead of 750 - and stalling. Dealer could find nothing wrong, so I changed the IAC myself. Car still idles a bit low, and still stalls once in awhile, but it's down to two or three stalls a week, instead of two or three a day.
I'm due for another service next week, so I may hammer the dealer on it again. If I get any further info, I'll let you know.
