My guess is there are multiple oil leaks going on and I am confident that the OP can do this work and save a f*ck-ton of money in the process.
My 2004 Yukon is just shy off 200k miles and I just fixed a few leaks. I replaced the valve cover gaskets, the oil pressure sending unit (because it comes with a new gasket), the oil cooler block off plate gasket, and the oil pan gasket, which had been seeping for quite a while. I also bought a rear main seal cover and installation tool but ended up not doing the rear main.
I did the valve covers and oil pressure sending unit one day and did the oil pan and block off cover plate gaskets another day. I tried to get the oil pressure sender without removing the intake but no dice. I pulled the intake and checked the valley cover and the crank or cam sensor next to the oil sender and both looked good to me. The oil sender was pretty wet.
The oil pan gasket was not bad at all with 4WD. Non 4WD is a walk in the park. The hardest part is snaking the pan back up in place with the new gasket, if you didn't rivet the new one on like I didn't. While I had the pan off I replaced the oil pump pick up tube seal just because. After all of this, if my rear main is leaking, it is very little and not worth the effort to pull the trans at this time. I did this work a few months ago and the engine is very clean. I saw a couple of trails but it could be from cleaning the engine. I used 2 cans of brake cleaner on it and then hit it with a can of engine degreaser and power washed it. There are no more drips in my driveway. Save yourself some money and fix this stuff yourself.