On the back of your motor unit near where all those white wires go you will find a button. Press and immediately release this and then walk over to your keypad and enter a 4 digit number of your choice. Press enter and you should be set.

This is generally caused by a bad bearing letting the sprocket lean forward and the chain jumps off. You can get the part at Sears or any opener service company. It is called a Gear and Sprocket assembly and the part number is 41C4220A. It should also come with instructions.

Make sure when you are programming the remotes that you release the smart/learn button quickly. If not you will erase what you have just done. What I normally do is hold the button down on the remote and then press and immediately release the smart/learn button. If this isn't the case then I think you have a bad logic board. I tried looking up the model numbers you give to make sure the remotes are correct but Sears doesn't recognize either model number.

Sounds like your door sensors are either misaligned or have quit. Make sure they are pointed at one another and the small light on each one is lit and not flickering. If you can't get the light to come on by tweaking them a bit then they are bad. The main light will blink 10 times and the door will reverse to the open position when there is a door sensor problem. You can get the model number off the opener. It's on the opposite end of where all those white wires go. It starts with 139. and you can use it at Sears parts to download an owners manual to PDF. You have to hunt a little bit to find it.