Ryland's right - the transmission is fairly light (~65 lbs), so putting it back in isn't that hard.
I imagine wiggling the engine off the transmission would be quite difficult, mostly because they have to remain perfectly aligned to keep the clutch hub from binding on the transmission input shaft as you separate them. There are a couple of guide pins between the engine and bell housing which will also probably tend to bind during the wiggling process.
When I changed the Blackfly's transmission, I left the engine in the car, and I had quite a time with the tranny (and it was
easier, since I was only wrestling the lighter transmission, not the heavier engine).
Don't forget to drain the transaxle oil before pulling the drive shafts from the differential.
