I've just been through conversion of my JAA CPL to FAA CPL, the process is not unduly complicated, but the securuty and registration process does take some time. I'd allow a couple of months. Once done your checkride, similar to an LPC is valid for 24 months.
If you've not done the JAA groundschool for CPL, the study for FAA may take you a bit of time too.
I am not exactly sure what you want to do but the answers to all your questions are in FAR/AIM, it's sort of like a more user friendly version of Lasors, with a load more info besides.
You can download it here:-
http://www.dauntless-soft.com/PRODUC...FQbUlAodWiKjIQ
or buy it from any of the usual pilots shops, make sure you get the 2008 version which is just out.
You can do your FAA PPL and CPL in the UK, but obviously it'll be a lot less in the states.
Meanwhile I'm off to Phoenix on 9th Nov to do my IR
