I feel you. I currently play piano, trombone, baritone, tuba and I learning guitar now. I've been playing trombone since 6th grade. It is pretty easy to pick up. Mainly you will need to get your lips strong and loose. Believe it or not poutting your lips (like a little kid) and blowing helps get those low notes. I don't recall any books right now but I'll something when I get home from work.
