BobVila.com

From my cross reference that is a billion code system. But by the date it should be a Security plus unit.

What color is the Learn button on the back of unit.

And I don't know anything about the HomeLink system.

You might want to contact the manufactor's tech support.

http://www.chamberlain-diy.com/diy04/contact_us/0,1341,uid-d2lqbWFnaWVibA==_1775,00.html

Or the tech support here.

http://www.aaaremotes.com/liftmaster.html

They sell the keypads on their website (as does Chamberlain). But I am afraid to give you a specific model number because I am not sure of your model.

Here is the Sears cross reference.

Billion code