Change Gearbox
 

Recently my E250 CGI, 2010 got struck due to transmission issues, gearbox was almost damaged due to coolant mixed with transmission fluid. Now I am planning to change it with used one, 72261807856667 this is my transmission number, I think this is 5 speed gearbox.

- what are things I need to check before buying a used gearbox ?
- is there any compatibility problem if I buy gearbox from same model car ? how can I resolve these compatibility issues ?
- will it require coding after replacing the gearbox ?

please forgive my flaws, I don't have much mechanical idea about MB