2000 Pontiac Grand Am 2 door 4 cylinder - Medium Oil Leak

My 2000 Pontiac Grand Am 2 door 4 cylinder has been leaking oil for about four months now. After I park my car, the oil spot left the next day is about 18inx8in, so it does not seem like a huge leak. I can see the oil dripping off the front of the oil pan when I first park my car (and the oil is still hot). When I look under the hood, I can see that oil has leaked out of the area that is covered by the Twin Cam metal plate. It leaks out one side and then must drip down. I have seen that I likely have leaky valve covers, but I've also been told that it's probably the head gasket starting to go. Is there a way to know for sure? I'd like to get a better idea for myself. Thanks.