2001 Ford Mustang

Can someone help me out with this. I had the same problem as some others with my 2001 Mustang GT stalling out as soon as I take my foot off the gas. I brought it in to a mechanic who said it needed a new IAC valve. He charged me 159 just for the part. Does this seem high? Im worried becuase I never had any problems with the car until I took it to him to have a tune up done last week. Then 4 days later I have to have it towed because it keeps stalling out. The car does have 80K miles on it but still, it seems odd. What do you think?
October 8, 2007.

More to the point is does it run OK now? 159.00 for the part and labor is OK. And it really could be coincidental.

Oct 8, 2007.
It seems to run OK, but I just picked it up today. Does it seem odd that it would need to be replaced instead of cleaned like I have seen suggested to others here? The 159 was just for the part. Labor was additional.

Oct 8, 2007.