First Question, you can upgrade to a upper edition with some discount later.
at this page :
http://www.conitec.net/english/gstudio/order7.phpthe third price line is for prices of the upgrade from lower edition.
If you dont want to be limited and not sure if you are going to use alot, get commerical version ($199?).
getting help. Forum is always here. You can check latest AUM's(older aums uses older versions), and the lite-c workdhop, other than that, there is a lot of open sourced complete games which you can learn from. And the manual, it's great, one of the best documenting style i ever saw.