Can you activate the phone after updating the ROM

[sdsoundguy2007]

I am kind of new at this was wondering can you do the Sprint Radio update on the phone load in your custom ROM and than activate your phone. Reason I am asking I am new at this did not see it after searching for a while. I have a new XV 6800 coming sometime today needed to know the best way to do this. Also any recomendations on which ROM?

Thanks in advance any help or advice or even a point in the right direction I could get would be greatly appreciated.