For the first time in my life, I am replacing on my own my 1/2 HP
LiftMaster motor with a 1/2 HP Craftsman motor. It looks pretty
straightforward - the mounting holes appear to be the same on both
units, the wiring is identical, etc. However, being a first-timer, I
have a few common-sense questions that I wanted answers on before I
proceed:

1. My starting point should be loosening up the chain so I can lift it
off the top of the old motor, right?

2. The motor is bolted to the ceiling brackets and the chain rail. The
ceiling brackets are no problem - but the rail bolts - if I unfasten
them to remove the motor, how do I keep the rail from dropping to the
floor and getting bent? Should I jerry rig some kind of support, like
holding it up with a bungee cord tied to the ceiling brackets?

3. Once I install the new motor and put the chain back on its sprocket,
how do I start adjusting the door - should the door be closed, then I
engage the chain? Or should it be open? How do I position the chain so
the door latch will engage at the correct distance?

I have the manuals for both the old and new units but for the life of
me, they are not very good in explaining in simple terms what the step
by step procedure should be for motor replacement.

Any assistance will be appreciated. Thanks much.

FT