Well im going to start building a 2x12 cab soon and I have a question, for the head to attach to the cab would a phone jack work or do I need something specific and should I run it out the back of the cab?

no, you would need to get a 1/4 inch audio jack... just like the one on the amp to plug a speaker cable into.

do you know what you're getting into?
My Guitars:
Gibson Les Paul Studio
Epiphone AJ
Ibanez Strat Copy

Orange Tiny Terror Head
Old beaten up Peavey cab
Marshall MG30DFX