oil leak on 1998 Honda Civic

I had my new cluch and rear main oil seal re-placed. the warrenty has expired and their is still some oil leakage. what are options. I add about two quarts between oil changes at 3000 mi. Should i use an additive oil gastkit sealier?

could anyone of the following
-Rocker cover gasket
-Cam or crank seal
-Oil separator system or o ring
-Sump gasket
-Oil pressure switch
-Distributor O ring