is the leak coming from any specific spot? usually if it's a cam seal leak, then you won't really see it leaking (depending on how bad it is) when you have a cam cover on. my old Mirage had a bad cam seal and i lost the cam cover when i replaced my cylinder head and shot oil all over the underside of my hood. wasn't too bad to replace tho. if you do replace em, i'd do em both. save you some time and effort.