BRAVO! The hard part in now over! Now tomorrow to finish up with all the details! Your tale reminds me of back when I was in college in '82. My next door neighbor had to swap out the blown TH350 in his 70 Impala 4dr family hauler and go to work vehicle. It was late December and we were working in his open, unheated garage in about -15° weather at night with a single drop light to see by and a small space heater blowing warmish air under the car, with the front of the Impala up on car ramps. While he and his cousin dropped the driveshaft and disconnected linkage, wires and bellhousing bolts, they slid it back and I bench pressed it down and they then pulled me out from under the Impala on the creeper with the transmission on my chest. Installation was pretty much the reverse, except when they went to reinstall the driveshaft, discovered that the parts yard used TH350 had the wrong length tail shaft on it and the driveshaft was too short!
So, remove the new tranny the same way old came out! I let him take my '72 BBC Monte Carlo to work the next morning, and when he came home from work we loaded the replacement TH350 into my trunk to take back to the parts yard to exchange for a tranny with the correct tail shaft on it. Then we repeated the dance of the night before and everything bolted up after I played Transmission Jack (Jack not name, Jack job!) for a second night in a row (and even colder than the night before!). Topped up the transmission fluid and he backed it down the ramps, out the driveway and a trip around the neighborhood, mission successful!
I also used the bench press method to drop the transaxle out of my '80 Subaru 4x4 hatchback when I needed to put a new clutch in it at 160K miles and to then install the transaxle back in back in '91. That was a lot easier as it weighed maybe 100 lbs as opposed to the TH350 that probably weighed at least 150, and it was 85° out, not -15° and -18°! I also used the bench press method to install a new clutch in my mom's 80 Datsun 510 4dr hatch 5 speed in her driveway later that summer. That transmission maybe weighed 75 pounds. It had about 145K on it at the time.