Oil plug has been out all night. I just put some water in at thermostat and it didn't take long until it was dripping out of oil pan. I no mechanic but believe the intake gasket is doable by me. The head gasket would seem out of my ability. If it is the intake gasket how is the water getting into the oil? I didn't think that oil went through the intake to be able to mix.
No, oil doesn't go "through" the intake, but the intake gasket does seal the intake from the lifter valley, but it is possible (and very common on this engine) for the gasket to leak to the inside, to the lifter valley, rather than to the outside, or to one of the intake ports.
If you poured water in, and it leaked out the oil drain that fast, I doubt it's the head gasket, the intake gasket is more likely as it would have a fast route through the intake, down the lifter valley drain holes and out the pan.
Go ahead and drain the coolant since you know you have a leak somewhere anyway, carefully pull the intake, trying not to spill too much additional coolant. If the lifter valley has puddles of coolant or water, there's your issue. Replace the gasket and reassemble, hoping you didn't have a blown head gasket as well.
Make sure when you get the gasket to get only either Felpro or ACdelco/GM. The gasket should be hard black plastic with either a red/orange or black "o-ring" around each port. Be absolutely sure not to use an all rubber, fiber, or cork gasket. Be careful because both Felpro and ACDelco/GM still sell the old style, (rubber/fiber) that you are probably going to pull off. You do not want that style again.
