Is your IAC bad? If it is bad or not working properly you will notice either a LARGE (almost dying) decrease in engine RPM's while coming to a stop or a VERY high idle. You should also have a code setting for this to be found. Also even if your IAC is bad your basic tune up :
Plugs (Compression test on each cylinder included)
Wires (if needed, most times are not)
Fuel Filter
Air Filter (if needed)
Check fluids, belts, hoses (if it has a serpentine belt it may need replaced)
Other than that the IAC shouldn't be a "TUNE UP" part. It is either BAD (which your car would run like junk) or it's not.
IMO- Get a second Opinion
ASE Certified since 1995 "Engine Performance" first test taken.