Good luck w/ that. A contractor is a pro. Hes not going to make any money from that, which means that youre not going to get his full attention once he realizes you don't intend to hire him.
Your best bet is to take your diagram down to Home depot, and talk to their 'master electrician' They started the program early last year (I think it's still on, but I don't work there anymore), and supposedly they have a certified electrician in every store (plus a licensed plumber). Since he's getting paid hourly, I'm sure he'd be happy to talk for hours with you!
Also, if you can find the store's "go-to" guy (there's usually 1-3 (out of 150-200 'associates'

in any given store... just a matter of finding him), he's the one KNOWS it ALL, (usually an ex-contractor) and if he doesn't know it, not only will he admit it, but he'll walk you too the person who does.