Musicman,
In addition to the good recommendations above, Paasche makes a great basic airbrush too. It's a single-action brush, so it'll be a bit easier for a newbie to use. I bought mine twenty years ago and still have it on my bench beside my newer double-action brush! The Paache H (siphon feed) brush sells for under $50 (including accessories and extra bottles) from Dixieart.com.
Hope this helps. An airbrush is the one tool that can definitely improve your modeling skills. Be sure you practice, practice, practice on old models as you learn this new skill. Every hour spent will be worth it!
Dennis