Rooting Phone before Mexico

A

AC Question

Hello!
I currently own an unlocked gsm phone (previously Verizon), I activated it with Metro PCS last year. I am planning to go to Mexico and I bought a TelCel simcard and an international plan to use my phone for a week in Mexico. I had a few concerns about that though. I was told that when I get back I can just pop in my previous Metro PCS sim card and continue using it like normal. Is this correct?
Also, I would like to root my phone but was wondering if that would have any negative effect on my phone since I w poo uld be doing the sim card switch. Would I be blocked or something? Or would there be any problem with my Network when I try switching back into my old sim card? Any help is appreciated!! Thanks!