Yes that would be the way to go I can vouch for the IBM X60 the on board wireless cards inject and thease notebooks can be picked up quite cheap now they run very well with just 2GB Ram I have 2 both duel core 1.8 and work very well with Back Box Linux and Kali Linux and as z3rocool states the Alfa AWUS036H is excellent, and if you want a good book to read on Aircrack-NG get yourself a copy of Vivek Ramachandran's book BackTrack 5 Wireless Penetration Testing, excellent book to get you started and you can do most of the lessons with any distro that has Aircrack-NG installed.
If you cannot get