The lettering looks good on the S197 generation but IMO not on the S550 version. The cars start looking way too busy adding letters and adding R to the fender logos etc. That's just me. I understand the "need to personalize" but everyone does the same thing and IMO its tacky. The factory design...
IMHO its a douche bag move to keep it and try to sell it to the new owner or anyone for that matter. It belongs with the car. You sell or trade the car put it in the trunk.
Trading in one of these is a waste of time. You will never get what its worth. Better off selling it privately. The only advantage on trade is the tax savings.