Did you have the center section out recently before the leak started? Probally not, huh if your asking how to take it out
Look very closely at the leak, make sure it is NOT leaking between a stud and the nut on it then leaking onto the center section
This can happen when one of the studs is knock loose or removed and reinstalled with no sealer around the serations that hold the studs into the housing
If it is leaking from the studs you may have to reseal that stud. I have been able to drain the rear end, clean the stud up real well with brake cleaner and then use thread sealer (or gasket making silicone)around the stud and between the copper washers and the center section
That doesn't work all the time if that is causing the leak, the other option is to seal the stud with silicone and pull it up tight with washers and a nut, let it sit overnight or longer to seal up. If it is something else, like the gasket, repair as needed
To answer your question on the axles, you do need to pull them out before trying to remove the center section
Buy a factory service manul for your car before starting, there is a adjustment on end play on the axles that needs to be checked and set if needed