From the sound of it you'll have no choice but to hire on a consultant to work out a project plan for you on a system akin to the NEC.
HOWEVER...good luck finding someone to be a "bounce" with out paying $$$$$$$$$.
You can find many a person (myself included) who are more than willing to help you write up a proposal. Even this board will answer basic questions, but to be a "crutch" is a risky business for any of us in the consulting field. We can't afford the hit to our reps. if you misinstall or cause a problem, know what I mean?
I'm not trying to say you don't know anything, as you obviously DO know alot, just not telecommunicaitons/PBX.
It reads to me what you REALLY would like is a personal tutor, which on the one hand is great, as you would like to learn hands on (as most of us did) but the cost of that (as I doubt you'll find any willing to aprentice you for free) is prohibitive.
Basic questions, or even the "Why didn't this work, this is what I did" is what this site exists for, so ask away at will (and (somewhat) free of charge).
Otherwise, I wish you the best.
Cheers
