I don't think there is a utility for auto-requesting songs through AIM.
Others can be found in the toolbox.
Check out the Sticky post titled...
SHOUTcast: Important Info & Answers to FAQs. READ ME!
Scroll down a bit and look for the section titled...
General SHOUTcast Information -> SHOUTcast ToolBox (All sorts of nifty add-ons for SHOUTcast)