From first hand experience, I can say that Mercedes will never sell that chip, if they have stock of the clusters, they will charge you both for the cluster and to program it separately, if you get a second hand one though, you can transplant the eeprom and it will work the exact same, milage and all.
As for fixing the pin, If you don't get greedy its not that hard, just find a single strand of the thinnest wire you have, tack it on the board then try and tack to the remaining part of the pin in the plastic, if things get really dire you can file down, but that is really getting to last resorts,