My understanding, based on some prelim research, is that if the used unit has the same part #, it will work BUT you should never bring it to a dealer, because it will come up as a "mismatch" and there may be legal implications.
But really I can't say for certain. Have you considered having your old unit refurbished?
Have you priced a new one at the dealer (they re-code new ones for you)? I think it's something like $350.