It's not too hard. But you'll probably swear a few times. Change the motors, wire harness, and relays. The 87-88 relay box mounts under the port fender, in front of wheel well liner, and directly accross the frame from the headlight. The only real pain is threading the wires up front near the radiator. You may find it easier to pull individual wires out of the loom, then push all the harness thru one at a time, and put the wires back into the flexible conduit when in place.
Scott
Edit= All the above is correct if you're exchanging the 87-88 harness in a 85-86. 84s have a different fan set-up, and I don't know if the 87-88 harness will run it properly. Personally, I'd invest the $100-200 in a full 87-88 headlight conversion, before I'd put close to $100 in rebuilt early design headlight motors.
[This message has been edited by AnimalGT (edited 01-19-2003).]