It seems to not turn off, keeps buzzing, at the end of the raising or
lowering of the door. I twiddled with it once to get it working again,
but now its cold it has failed twice this month same way.

My question is, are the replacements simple enough to do? I don't need
to touch the door or tracks or springs, but I have never done this
before. My current one is a chain drive All-O-Matic. Inside the box
there is a motor driving a wheel with a belt. The door is a double.

Any recommendations?