Changing ROM, different carrier from original, will it have to be reprogrammed?

[Tekzel]

Hi, I have searched and searched for the answer to this, didn't want to ask it and have the answer right in my face!

I have an HTC Touch VOGUE from Sprint, that had an Alltel rom written to it then reprogrammed for my carrier, MetroPCS. The guy I got it from said they did it that way because Alltel was easier to program or something. He also said these particular devices have problems with WM6.1 and thats why it only has WM6 on it and he didn't recommend me upgrading it. I kinda doubt that, but maybe someone here knows if this is true?

Anyway, the question is if I DO upgrade it to WM6.1 or wait for a custom WM6.5 rom when it is released, will I have to reprogram it for MetroPCS after the new rom is installed, or is it only the USER data that is wiped by the rom upgrade? If the carrier configuration is overwritten, can I just go in and write down all the data and then after the upgrade go back in and plug it all back in (maybe there are only certain fields I need to record?) and have it work on the new rom?

Any help would be hugely appreciated! Thanks in advance.