Using Different Carriers Phones With Your Current Provider?

My title my be a little obscure so let me explain. I currently am a customer with U.S. Cellular, a CDMA network (obviously). My current phone is a little messed up, so I was looking into getting another off the internet. I have a Nokia 6265i, dropped it the other day, screen back light comes on, but no display , tried a new screen and flex cable, no luck. So I figured I'd go on ebay, get another CDMA 6265i and have them swap the ESN over... I was told by one rep, that as long as it was a CDMA phone, it wouldn't be a problem, but a service tech, said it HAD to be U.S. Cellular carrier or I could risk being in roaming if it was activated. From what I read, each phone is assigned a 5 digit FCC number (SID) which corresponds to the carrier they are with. Allowing towers to differentiate between roaming phones and non-roaming phones on their networks. My question is simple, is this true or not, if I get say a Metro PCS phone that is a 6265i CDMA phone... and it's activated by U.S. cellular for me, am I going to have problems or not? Or am I going to just have to get one and see what happens. Unless of course the SID is not hard coded and can be hacked and overwritten? Which I hope it is, since it would seem easier for Nokia to just program them from the factory then make individual chips for each new carrier on the market. I wouldn't mind hacking my phone up, always a fun time. Hopefully someone can answer this for me.

Thanks!

I see a lot of views, but no replies... Maybe posted in the wrong section?

Bump!