New Antenna Troubles

Hello Celica Buds,
I have a 1998 Convertible that has a busted mast on it's power antenna. I thought I would try to replace the whole unit with a "Metra" brand power antenna replacement.
The problem is that the old unit had a relay box that connected to the main harness that runs into the trunk. That connector has about 6 wires on it. Comming off the relay box is a 2 wire connector which then plugged into the old power antenna's motor. That motor plug was keyed so that it could only be plugged in the right way. The Metra unit only has 3 wires on it that can be hooked to anything (besides the antenna wire itself). I'm not sure what wires on the metra unit hook to the old antenna control relay,... and since I'm replacing the old antenna do I even need all that old wiring?? The wires on the Metra unit are Black ( which is chassis ground), Red (which is supposed to be hooked to the always "hot" wire), and Blue (which is supposed to hook to the "radio on" wire).
I've managed to mount the thing to the fender fine, now I just have to make it run up and down. Has anyone done this before or can offer up a useful tip to help me out as to how I should wire this puppy??