Where can I get directions on how to replace a tail light lens on a 1984 Lincoln Town car?

 

Most times, it's a waste of time to swap the lens. Get a used lens and housing from a junkyard and install the whole thing. A new lens/housing from Ford (if still available) is probably a small mint.

Most times the housings and lenses are glued together with sticky caulk and adhesive and it's a gazorch to remove it all. You have to use a razor blade to split the caulking, reseal the new lens, etc.

If you mean replacing the housing and lens as a unit, usually if you pull back the trunk liner you'll see the bolts/nuts holding the lamp to the body.