I'm just getting new 7.7, really eager to root my tab, but when reading throughly, it seem that will void waranty

Is anyone know how to unroot it back if there is anything happen to my device that i need to sent it to svc center?

It looks like message and phone a bit slow to load up when i open it, around 10-20second, and sometimes dialog box to force close it came out, any idea?