Gatorgabe

Hey all ... I have my mom's 2003 E500. The car has only 42,000 miles, but the passenger side seat adjustments haven't worked for about 2-3 years. My brother - an ASE-Certified mechanic - always said the control module under the seat was the problem, but he never took the time to fix it for our mom (long story). Now, she has come up to live with me and we want to get the seat fixed.
So I purchased a genuine OE replacement module from German Auto Supply in North Carolina. I took out the old module, gave them the part number, and they sold me the newer part with the newer part number. I gave it to my mechanic here in Nashville (a very good mechanic) and he replaced the module, but the seat still will not adjust or move in any direction.
Any thoughts on what to do from here? He's already checked all the switches, etc. Wondering if the module has to be programmed before installation? I was told by Mercedes in Atlanta that the module should be simply "plug in and go."
Is this correct? What are we doing wrong? What are we missing?
Any information at this point would be extremely helpful. And thanks in advance for your time.