The nearest thing the Crossfire has to what you are describing is the SKREEM module.
Failures do happen, but that is somewhat a rare occurrence. The dealer must order the SKREEM based on your VIN, no programming (other than the lock/unlock buttons on the key fob) is needed.

Used parts or Mercedes parts will NOT work, it HAS to be a "Crossfire" version of SKREEM with YOUR VIN in it, so you have one option here. NOW, beware that horror stories have been told of people going to a dealer for a SKREEM and after 1-3 weeks, then being told the PTCM is bad - and for $3300-$3500 they can have their car back. HOPEFULLY, your dealer knows what they are doing, and they get it right the first time.

What symptoms brought you to this point? (Asking because I dont' trust dealers)