OK, Here are some pictures of my set-up. Difficult to get good pictures in a cramped space. Basically started with an old garage door opener that I took a section out of and made it shorter. Mounted in the same manner as for a garage door and tied a piece of rope to the tram.
Mounted a clothes line pulley at the end and extended the rope down to th door that just slides in a track.
Wired the push button through two X10 universal modules (one for open and one for close) that are plugged into outlets near the opener.
Universal modules are run through a magnetic proximity sensor so that a "close" only get to the opener if it is open and and "open" only gets to the opener when it is closed. Allows for controller to send a command multiple times without having to worry about flip flopping the door. This is important because the X10 protocol travels through the normal AC power lines and depending on noise (or collisions) a command does not always make it. Nothing worse than sending a command to close the door at night and find out the next morning you actually opened it.
Only issue I have had with it is when debris gets piled up high enough under the door and prevents it from going down far enough to trip the proximity sensor. A once every couple of weeks scrape with the shovel prevents that.
One nice thing about a drop down door is there are not a lot of edges for bears (and/or other critters) to get a hold of. With any luck, the extra challenge frustrates them enough to leave.