1. Depends on your aptitude for theoretical learning, but integrated with your flying or a crammer course halfway through is my preferred option.
2. Trevor Thom I found to be more comprehensive, but I guess it also depends on whether you want to go further than PPL.
3. I'd go with everyone else here and say wait until you are into your training to ensure you really enjoy your flying.
4. If you want to drop me a PM I can give you some details of ground school training organisations. You will need to enable your private messaging facility or leave me your e-mail address.
(Hit the Private Msg button between Profile and WWW buttons above and go from there).