[For 1.6] Advanced Invitations System v1.1.0

[Dev Guy]

Hello there!

I want to know how can I change 'user?action=advinvsys' to something like 'user?action=sometexthere'.

Also, I want to remove other payment systems except PayPal completely. How can I do that?

Last, but not the least, please guide me on how to add any other kind of payment system (like Bitcoin).

Thanks a lot!