This is the problem with the V8 engines and the transmission pan, see first picture below. The exhaust cross over pipe from the drivers side runs directly below the transmission pan and required the drivers side Pre-Cat O2 sensor to be removed and the front exhaust needs to be disconnected at the manifolds to drop down enough to get the trans pan out past the exhaust cross over. It may be possible just drop the exhaust the length of the studs and try to pry the exhaust down, but it is not worth the hassle. The exhaust has a flex joint after the "Y" comes to a single pipe and it is fairly flexible. Just need to drop the front of the exhaust down about 3 inches and the trans pan will clear.
The filter stupid expensive, around $107 list price, I do not recall the exact price I paid, I think it was around $70. The gasket is reusable, but is probable around $70 list price. Fluid would not be to expensive because you will only get about 5 quarts out dropping the pan, but GM charges about $12 per quart, the best pricing I have seen is on Rock Auto and a 12 quart pack on my doorstep was $80.61 shipping and tax for $6.72 per quart of AC Delco ULV transmission fluid. But the dealer quoting $1100 is also way out of line. I pulled my valve body and installed the NextGen valve body upgrade kit with the truck up on ramps in the driveway, I could probably drop the exhaust and change the fluid and filter on by back sliding back and forth under the car in about 2 to 2 1/2 hours. The dealers is quoting from a flat rate labor time guide would be my guess?? I would search out a really good independent to do this trans service and install an aftermarket pan like I did. I would probably also steer clear of national transmission chains as well like AAMCO, they will likely screw you as well. The PPE holds 2 1/2 more quarts of fluid. Just make sure you get the proper pan because if has to clear the exhaust, the pan for the 6 cyl Diesel and some of the non 4WD trucks does not clear the exhaust. The PPE trans pan was right close to $300 for the proper pan to clear the exhaust on the 1500 V8 4WD vehicles.
The correct PPE transmission pan with the clearance for the exhaust cross over pipe on the V8 1500 4WD trucks is PPE#128051300. Be careful when searching, the PPE#128051200 is not the correct pan. The descriptions are a bit poor. I think the 10L1000 "Allison" transmission has a large pan perimeter and it does not have exhaust clearance and there may be the similar pan with a slightly different part number PPE#128051100 without the exhaust clearance that will work for the 6 cylinder Diesel in these trucks.
Since you tow, I HIGHLY suggest you get an aftermarket trans pan like the PPE unit with a drain plug so you can easily drain the fluid without dropping the exhaust. The older the vehicle, the more chance to break and exhaust stud!
Setting the transmission fluid level is critical and there is SO MUCH BAD INFORMATION OUT THERE ABOUT HOW TO DO IT AS WELL AS THE GM PROCEDURE SUX AND IS SUPER DANGEROUS TO THE TORQUE CONVERTER AND THE PERSON FILLING THE TRANSMISSION. If the valve body is not removed, the cooling circuit does not drain and setting the level without a modified valve body will be easy. No need to raise the transmission temperature to over 175F by power braking/brake torqueing and getting the exhaust cross over pipe cherry red. ALSO THE FLUID LEVEL MUST BE FINALIZED WITH THE ENGINE RUNNING, IGNORE ANYTHING ELSE ANYONE TELLS YOUR OR WHAT YOU READ.
I would also recommend installing a heat shield on the exhaust cross over pipe because this pipe is Post Cat and can get stupid hot and turn red under heavy loading and transfer this heat back into your trans fluid. See 2nd picture.
Suggest you look over this thread of mine for more info -
https://www.tahoeyukonforum.com/thr...peed-valve-body-kit-finally-installed.153898/