Revert EVO 3D back to Sprint

[VictoryPanda]

I see there's the sticky topics at the top, but I'm afraid that they might not be what I need and I'll end up messing my phone beyond repair. I just hair a fairly simple request of help. Basically, I brought an EVO 3D from someone and I didn't know it was rooted to Sanyo or whatever. I'm trying to activate it with Sprint but I don't know if I need to root it, unlock it... or what. I've tried google and youtube and reading other people, but i want to be sure that I'm doing the right thing for my phone specifically. Pleaaaase help me. ): /supernoob.

In a nutshell, I want a Sprint EVO 3D and that's it. No roots, hacks, bugs, anything.