I just installed one of those kits from PonyPerformance.
The module takes 15 minutes to install, or 30 if it's your first time and you're double and triple checking everything. Installation was really simple. Pry open the top part of the trim that holds the window switches, then pull the entire trip piece up. There's one clip near the rear end holding the trim piece in. Find the right colored wires and tap into them using the connectors provided. There were two or three wires to connect using crimp on connectors. There's one wire to cut and two crimp on barrel connectors are provided to make clean connections. One wire had to be grounded to the door. I attached the loop fastener (also provided) for the ground wire to an existing screw in the door. The only tools I needed were a flat blade screwdriver to pry the trim away from the door, a crosspoint screw driver to attach the ground wire, and a wire stripper/cutter. I also used a multimeter because I was paranoid and wanted to double check all my electrical connections. The control module itself does not have to be attached or bolted to anything. I just wrapped it in one of my spousal unit's socks to prevent any rattles, and lodged it between the door and the trim.
Once installed, I can click the either switch (driver's door or passenger's door) for the passenger side window and it will roll all the way down. Pressing the switch again while it is rolling will stop it. It does not have a one-touch UP mode. I personally consider that to be a choking hazard.
The instructions cover both 99-04 and 94-98 installations. The kit costs $27 shipped. The website only takes Paypal, which I don't have so I mailed a personal check and received the kit in less than a week. The owner of the business is really good at responding to emails.