Heads-Up is my favorite game type as well. I have realized best way to learn heads-up poker is by volume, playing lot of
hands. That's why I can recommend Advanced Poker Training, there you can choose between cash and sit and go heads up.
Heads up is a very stressful game. Good concentration and tilt control are must to have, both are learnable skills, so no worries..
Phoenix Wright had a very good answer. First learn basic guide line like charts, and then become more independent and abuse your opponents tendencies when you go upper to the stakes.
Anyway, I have got great results by using just APT, there are many different opponents to play against, so IMO you don't need anything else than APT and a lot of volume for Heads Up to make some serious money, or at least it worked for me.