As someone who changed his own clutch mostly by myself, I can say that the engine support tool would have been helpful.
Basically, when you remove the pitching stopper, the engine/tranny can tilt forwards and backwards freely. When the you're trying to remove the transmission, or trying to line it up to put it back in, any movement in the engine can be annoying, since there's binding on the input shaft.
I used a ratcheting tie down strap to hold the motor, but it still allowed for a lot of motor movement. If you're creative, you can hack together your own engine support assembly tool.