O.K., I lied. I have a fifth question!

I have approx. 2,500 miles on my new Volvo-rebuilt B230FT engine that I recently put into my 1987 760-Turbo and I'm still having a stalling problem when I pull up to a stop. The RPM needle momentarily dips down to around 400 RPMs for a second, then surges back up to the 700 or 800 RPMs that it normally sits at. Most of the time it just stumbles through this, then idles smoothly. But probably 10 or 15% of the time, it doesn't recover from the 400 RPM dip and just stalls. Annoying, to say the least (especially for the money I had to yack-up to the Volvo dealer's parts dept. for this engine!!), but I'm also concerned about letting my wife drive it. I can just see her stalled in the middle of an intersection with a giant coal truck bearing down on her ... hey... wait a moment... on second thought, maybe there isn't a problem afterall !!

No, seriously, all kidding aside, I really want to solve this problem before I officially allow her to drive it around with my daughter in it. The mechanic who helped me install the engine (who also works at Volvo during the day) thought that the idle-speed motor may be going, as it looks like the original one (204,000 miles) that came with the car. Is this an easy change-out? It doesn't look too complicated. Are there other things I should check, as the engine is still really just breaking in yet. I hate to spend the $160-or-so that Volvo wants for a new one, just to find that it was something much simpler that was causing the stalling. Is there an aftermarket source for these idle-speed motors? Let me know!