Get the plug n' play harness for the particular timer and its as easy as that.....plug n' play usually the harness can be had for an additional $15-$20 on top of the timers price. On most cars, the timer plugs into a small harness found near or around the steering wheel column.
werd, get the harness. And if you can use a screwdriver, you are all set. The hardest thing to do is to hook up the ebrake wire (which is easy). Just be sure to get the correct harness for your year. They changed somewhere in 89. A word of caution: if you car is an 89, check the plug before ordering the part. Get under the dash and take the panel off. You should see a bundle of thick black wires leading over to where the key goes in. Removing the plastic air vent will help you see it. Find the connector. If your connector is 4 pins wide (like mine was) you will need the 87-88 harness. Is it is 6 pins wide, you will need the 89-92 harness.