I did this upgrade a couple years ago and it took all of 15 minutes from start to finish. Basically all you need is a switch and switchplate for the dash, a trunk release relay (horn relay works also and is heavier duty), trunk lid wiring that runs through the trunk itself, and the release solenoid.
Basically all the wiring is present except the additional wire running through the trunk lid that attaches to the solenoid. In that event you have a couple options, the easiest being to replace the harness with one from a donor that has the solenoid wire, or remove your current harness and add an extra wire. Just make sure you get the switch, switchplate, solenoid and attaching screw, or whole latch if you prefer, relay, and trunk harness (optional but recommended). I have to say that out of all the upgrade projects I've taken on this was by far the easiest.