Oil on alternator

[smerf]

I recently had my alternator replaced (93 maxima). When i looked at the alternator before taking it to the shop it looked brand new.... but when they gave it to me to swap out (warrantee) it was absoultely covered in oil. I had a hard time getting the parts store to replace it because they claimed the oil ruined it... which seems like a logical conclusion based on its appearance. Is it common for an alternator to get oiliy when removing/installing or is it likely there is a leak somewhere? Is there perhaps a bolt or plug which needs to be sealed to prevent leakage? I would hate to ruin another alternator.


Thanks