I fixed my 3.1 oil leak last night. This is the common leak that is on top of the engine around the "distributor block off" plate. This cover is actually the top of the oil pump drive shaft assembly. I'm going to do a full write up, maybe it will end up in the "How To" section. Here's the short version: 1. Remove the throttle body including the heater hoses (this was a PITA, I cut mine off), remove the electrical connectors, leave the cables on, move the TB out of the way. 2. Disconnect both fuel lines at the fuel rail and lay them out of the way. Be sure to de-pressurize the fuel system. 3. Remove the "C" clamp that holds the oil pump shaft assy. 4. Pull out the oil pump drive shaft assy. This is basically a shaft/bearing thingie such that the shaft has a gear on one end that meshes with the camshaft and a 6 sided allen wrench-like hole in the other end that couples to the oil pump. 5. This assy has an O-ring on it, my O-ring crumbled when I tried to remove it. This is the O-ring that needs to be replaced. It was $2.60 at my Chevy dealer. I put the whole mess back together and no oil leak! You'll need some antifreeze and I also replaced my TB heater hoses. Took about 2 hours.