Are you sure its oil and not just crud and grime collecting because of the coolant leak? I would stop riding it right now also, that coolant is destroying your pistons if it is getting in the cylinder. It will eventually cost you lots of money. And definately don't use two gaskets. You are going to need to pull the jugs off(at least) and inspect it further. If nothing else is wrong other than a leaky base gasket, and you haven't destroyed anything yet, check to make sure your mating surfaces aren't warped and put in the new gasket. Torque and retorque as everyone else has instructed you to do, should be good to go.