Just did the swap and change on a 2018 Sierra eAssist with 8speed. Note that the exhaust actually runs across the front side of the pan (near the sway bar) and not the rear. Also, the only thing preventing the pan from coming out is the transmission filter. Just wiggle, some muscle and it will come out, or maybe pull out the filter while the pan is still on if there is enough clearance.
I pumped out 5 quarts only, but had already filled it back up with 7.4 quarts before checking the waste container. I ended up having a lot of fluid (2.4ish) come back out during the level check. Makes total sense since only 5 quarts came out, but just make sure you check your level after if you didn't measure what you took out.
For those who have eAssist, deeper after market pans made for non-eAssist would likely not fit as the exhaust crosses over at the front of the pan and not the rear.