Yes it is. I've personally done it multiple times and it works fine. If I were you I would look into some ROMs like Liberty or ZombieStomped. Both work fantastically and are really easy to set up.
I did the same thing had to warranty out my DX the new phone came with gingerbread pre installed the old dx was rooted I sbf'd and factory reset before I sent it back! I'll wait for a root cuz I'm not having any issues with gingerbread. I don't wanna sbf back to Froyo reroot install the 2 part files and then I might have issues! But that's just my thing lol