Before removing it I'll want to flip the mower upside down. Do I first need to drain all gas and oil from the mower first? Even if I somehow manage to remove it without flipping, can I swap the deck without draining?Removing the blade adapter is likely to be difficult and require a two jaw puller to get it off.
If you search You Tube for "removing blade adapter" there are numerous videos on how to perform this trick.
To swap motors you basically remove the operator cable, put a clamp on the recoil start rope so it won't rewind back more and take the end off the handle bar, remove the blade, take out the three mounting bolts, trade motors. Sometimes the mounting bolts are a tough chore, as said before soak them good.