I'd just replace the IAC if you suspect it. As far as removing the TB and cleaning it, just remove the bolts from the UIM and pull the TB. Clean the entire thing until it shines (backside is typically the worst). Make sure you replace the gasket as well when reinstalling. You will loose a bit of coolant when you remove the TB.

YouTube search for GM 3800 throttle body removal. I'm sure it's there.