l care about how it looks, as well, l do not want a hack job that looks like a hack job, if you get what l mean.

I'd also like it to turn on and off when the trunk opens and closes.

Just use one of those as-seen-on-tv Stick Up Bulbs lol. Seriously, l think u could find a cheaper & easier alternative than installing a light back there.

You could always contact the dealer & find out about installing one correctly, part of the wiring is probably already there. Otherwise, maybe get a repair manual & see if it shows u how to do it, the book probably has instructions for repairing it, so u could get a better idea of how to install one. l have a light in my trunk, & it really does not show much! lol. It is pretty dim.

If there are wiring present then it is a matter of splicing something. Making it turn on when you pop the trunk open involves adding a switch or some sort.

l agree, use one of those stick-on thingies. Battery powered and so cheap, no point in spending money on something you rarely if ever use. You can always rig some sort of a pull switch if you really want to.

If you look in the trunk of a 96 Sable that does have a trunk light, you can see what the Factory version looks like. Then you can decide how to do it. Chances are, somewhere in your trunk is wiring system, is already a place to plug the light in. You would go to the Mercury dealer, get the light, and simply plug the wiring into the right spot!!