Casey
You take the screws out of the instrument cluster. 3 on top, 2 on bottom I believe. Then disconnect your speedo cable and wiring harnesses (2 each). Remove from car.
Remove the faceplate from instrument cluster, lay off to side. Remove 3 or so screws from where clock would be. If you have the same Jeep tach I have, you will have to do alittle work with a air grinder or a dremmel tool to make the tach fit. Mainly, most of the work should be at the top of the hole. Keep doing this until the tach fits in snug. Watch out for wiring harness on back of instrument cluster while doing the grinder work.
Once tach is in, check all light bulbs. I did not remove my blue globes like Jason did but I am sure that would be a good idea. Once ready, assemble back in car. The tach should hook into fuse panel (for power), one ground I think, and one to the motor. Do not use the wire labeled as lights as the instrument lights will be your lights.
If you have any trouble, let me know. I have actually done 2 of these now. Good luck. I think you will really like it!!
Paul