No. You CAN put it back to stock Froyo but your phone will probably, at some point, force the GB update on you anyway. But what you put on the phone doesn't really matter as you said you were bringing it back to VZW right?
Is it in need of repair or are you trading up?
I live life by three rules. Rule one, Sh*t happens, rule two, sh*t happens on a daily basis, rule three, get used to the first two.