Unlocking a phone, Okay cell phone guru’s, I need some direction.?

I have a Sprint branded Galaxy S ll Epic 4G Touch. I canceled Sprint within a couple of months, and paid Cricket to flash it, and canceled them shortly thereafter. Since then I’ve used it as a MP3 player, web surfer, and so on. I now have the code to unlock it from Sprint. What can I do to use it again, as I really don’t want to buy another phone when this one still works for me, as I doubt it would be worth selling with the $350.00 I had to pay for it? And I don't want to pay for another flashing,

Can I wipe all Sprint and Cricket from the phone now that I have the code?

I don’t want a contract service since I’m moving to the mountains of KY, and have no idea which services work there.