looking to buy another 12 valve. guy says it has a significant oil leak from the timing cover. is there anyway to tell if the timing cover is leaking from the inner without tearing it down?

 

I would like to sell my 1997 2500 extended cab with 336xxx miles that also has a oil leak at the timing cover.
Did you find a way to determine what seal/gasket is leaking?
I don't really want to repair it myself, so I'll probably reduce my $4500 asking price.