David,
The only difficult part was snaking the wire up and over the transmission.
When I disconnected the old sensor behind the front seats, I tied a string to the end and pulled it up and over the transmission housing. Then I pulled the new sensor wire back over with the string. Just pull gently and help it along with your hands, as there are a lot of places where it can get snagged.
Use jack stands, not ramps, and remove the driver's side rear wheel (G50 cars). You'll be able to see where the sensor goes into the transmission from the side of the car.
Actually, I had a hard time pressing the rubber grommet back into the hole in the floor pan as well, but eventually it went in.
The second photo shows the hole with the sensor removed. The sensor wire DOES NOT go through the plastic clip as shown. I just put it through there to keep it out of the way when I cleaned the magnets.
When you install the new sensor, put a little oil on the o-ring, make sure the area around the hole is clean and make sure the sensor goes in straight. I used a new spring clip ($6) and I put some Loctite on the bolt. It's a small bolt so don't over tighten it. The the wire goes up and over the top of the transmission and back through the floor pan into the back seat area.