There are tons of info on this subject and good advice too, do a search for threads containing Giving B/J or Giving head.
1 thing that bothers me tho about your statement is that he'd leave you if you don't do this right, if all it's about for him then I'm not so sure you'd want him, would you, sorry, felt I should be blunt here.
Also any girl that would want to practice on me I'd say bring it on, he needs an attitude adjustment!
It's just hard for me to understand that.