I don't have a Catalina, but I do have 1990 vintage Lewmar portlights, which have dripped on occasion. Cleaning the plastic lens and the gasket made a difference, but I haven't tried vaseline or any other kind of conditioner.
I considered replacing the gaskets but talked to the folks at Select Plastics, who encouraged me clean things carefully and only consider a gasket replacement--which is apparently a pain--only as a last resort. They do all kinds of hatch repairs and sell Lewmar hatch repair parts, but so far the only thing I've gotten from them is free advice which was helpful. You might check with them on the long term effects of vaseline.