winter project

Well got hold of a full front axle for my 200tdi (didnt realize quite how heavy they were.Going to be my winter indoor project, a full strip down clean up and rebuild with new bearings seals etc.My question is how can i check the diff is ok. It works i checked that before i bought it but thats about as much as i know about diffs. Any experts shed a little light on how to check it thoroughly .Thanks in advance.

check for play in the pinion bit that connects to prop...my knowlege is now empty