I just got done repairing some oil leaks on my 2004 Yukon 4x4, with the oil pan gasket being the last of the repairs being done last night.
I can tell you right now that I replaced the valve cover gaskets and the oil pressure switch first and that solved a lot of the leakage. You can see trails of oil all around the cylinder heads that will eventually leak down to the bottom of the engine. The oil pressure switch, which sits st the back of the intake, will leak down the back of the engine, imitating a rear main seal leak.
I have changed the oil myself on the truck since 2009 when I bought it so I noticed when leakage was appearing around the oil pan. So I decided it was time to fix all of this crap. 196,000 miles on it and no plans to get rid of it, so I ordered everything from Rock Auto. I even ordered a Dorman rear main seal kit and installation tool, but I don't need them now. When you pull the oil pan down, you can see the back of the flex plate and the immediate rear main seal area. Mine was pretty dry, so I am confident the valve covers, the oil pressure switch and the oil pan were the culprits.
So to sum up this novel I wrote... get a second opinion for sure. If you can spin your own wrenches, do this stuff yourself. It is not hard, just time consuming. You need to clean mating surfaces and you can replace other stuff while you are in there. Rock Auto has the best prices for this stuff. The only thing I bought locally was a new drain plug, just because, the oil pump pick up tube seal, which I read about after I placed my order with Rock Auto, 4 cans of brake cleaner and oil and a filter. I did the oil pan gasket last night and all I have left to do is spray some engine degreaser on the bottom end and hit the car wash. I sprayed a whole can of brake cleaner on it and let it run last night for 20 minutes and there were no leaks.