I lost my car key and had to use the spare key. So, i need to get another key in case i lost again.
What should i do? should i just get another key and ask Mercedes to reprogram the key or do i have to replace the whole key systems?

Also, can i get the key from http://getmercedesparts.com/ ? i believe that the part #2127601906 for 09 model. Not sure which one to get, bcoz there is a selection for master and emergency.

Any help would be appreciated. thanks

 

Call a dealer. The keys are programmed for your car only and you won't have to replace the controller until you have lost, I think, six keys.

Someone here a few years back bought a key on Ebay and then found out it could not be used.

The two keys are identical so I don't know where the master/emergency thing comes from. You also lost the blade key which can always be used to get into the car regardless of reprogramming. Unless the driver's door lock cylinder is changed.