This is not exactly a fun task but if you have a leaky gasket, or happen to rip it when dealing with either the rear main seal housing or the front timing cover, here is how I replaced it.
Prior to raising the motor you need to drain the oil then disconnect the oil level sensor wire and remove the sensor from the oil pan. Remove the dipstick, exhaust Y-pipe, starter motor, oil filter, and if you have an oil cooler you will need to disconnect it and move those pipes aside to get at the oil pan bolts. You might also want to look at the AIR crossover pipe and if it will be in your way, loosen the brackets holding it to get it out of the way.
I was able to raise the motor enough by jacking the motor using a block of wood (2x6) under the crank and the accessory mounting bracket. I used the car jack on a couple of 4x4 blocks to lift the motor. Be careful and make sure nothing will slip as you raise the motor, and also make sure of clearances needed on top of the motor and transmission.
Now you are ready to remove the motor mount through bolts and raise the engine.
I had the wheels on ramps and you will notice that as you lift the motor nothing appears to happen. The car is also going up as you unload the weight on the front suspension. After about 1 to 1.5 inches of travel the motor does go up without the car. Raise the motor as high as possible. Some people can remove the oil pan using this method but others, including myself, can't due to the clearances at the top of the motor and the top of the tranny. Each car is different.
One oil pan removel tip I learned after the fact is assuming you have the body on jack stands and not the front suspension or ramp like I did, disconnect the steering shaft from the rack and pinion. Loosen the 6 subframe bolts about 2 to 2 1/2 inches. They are fairly long and will let the cross member drop enough to remove the pan.
At the front corner of the oil pan on the driver side has a stud with 1/2 inch nut and a second nut that holds the bracket for the oil cooler lines. The passenger side front is a 1/2 inch bolt. The rear stud nuts are also 1/2 inch. All the rest of the oil pan bolts are 3/8 inch.
Remove the old gasket (feel free to cut it). You will need to slip it under the dipstick tube. Clean the pan and block surfaces. 1. This first picture shows the front of the oil pan after dropping the pan and removing the old gasket and cleaning the surfaces.
2. This picture shows the view from the rear after dropping the pan and removing the old gasket and cleaning the surfaces.
There are a couple of ways that were suggested to install the new gasket if you can't completely remove the oil pan. One method would be to cut the new gasket so it could be put into position and then seal the cut with RTV. Other suggestions made for this method included making any cut at 45 degrees to improve the repair of the gasket with RTV.
The other alternative is to slide the gasket around the outside of the oil pan and then work the driver side over the edge of the pan, then the passenger side over the pan, and finally slip it under and around the dipstick tube. This was the method I used and it worked like a charm. You just need to make sure that the oil pan is fairly clean so you don't drag road grim into your oil pan. I used the GM 10108676 gasket.
3. This picture shows the new gasket, pan, and pan support. The gasket was lowered and the RTV applied and everything was bolted in place (see below).
I put about 1 inch of Permatex Ultra Copper on the block each direction from all 4 corners. then the gasket, the pan, and the pan supports. Installed the corner nuts/bolts, and the remaining oil pan bolts. The corners were torques to 180 lb inch and the others to 100 lb inch.
I also installed a new oil level sensor since this was leaking GM 24507190. Per the included instructions, put a little oil on the threads and torque to no more than 9-11 ft pounds.