Exact same think happened to my 996tt from the hurricane. Immobilizer module and seat module dead under drivers seat. Seat module started smoking and burned badly. I disconnected the battery. Now, put your head near the floor and look under the seat and up. you will see 2 white hinge looking clips with a whiote plastic pin hanging down. this holds the lower seat cushion to the front seat frame. Pull the pins down and they will come out. Wedge a sma;ll screw diver under the white hinge clip that joins lower seat to front rail. Lever that clip downward and it will pop out. Do both of these clips. Then wiggle and pulll lower cushion up and towards the upright back part of the seat. Now you can see inside the seat. The second motor from the front does forward and back so you can move the seat away from the seat bolts that you need to remove.
There are 2 torx screws(t25 maybe) that hold the motor. Remove bolts and motor comes out leaving a small threaded rod in the mechanism that moves the seat. Turn this and seat moves forward or back depending on the direction you turn it.. Use a power drill. Tighten the chuck of the drill onto that threaded rod and spin the drill. Try forward or reverse depending on which way the seat needs to go. It took me 5 minutes to do this after struggling for 2 days trying other ways.
If you would rather jump the motor, then remove 4th clip from the end on the seat module. Please find the diagram to clearly see this. It has 5 pins on the free end once you detach it from the black seat module. one part has 3 connections and the other side of the clip has 2. Use the 2. One is a ground and the other the power. get 2 insulated wires. Put one wire in each connector again on the side that has 2 versus the side with 3. Hook a power source to the 2 wires. I used a battery charger. You can use jumper cables from the 12v battery in the car. I did both. Now the seat will move. If the seat is going the wrong way, reverse the connection to the wires. Just Put the one jumper cable on the other wire and vice versa.

 

Number 4 is the one to jump in the picture. It is LV. Use the right side of LV with the 2 wires. Put your 2 wires in these 2 holes and connect them to your positive and negative leads from your power source. Good luck. My situation is identical. Do I scrap the car and take insurance money? I love it. I have put a year of sweat into making this car my own. I have done all the work in my hot as hell garage in New Port Richey. This car is family to me. I hurt with you. This is the first time my garage flooded. Outrageous storm surge here.

 

Awesome and helpful response,Hamlet! I hope you both are able to rectify your vehicles…. All the best to you both!

 

If you have insurance, maybe save yourself some trouble and get an adjuster to look at the car or just talk to one on the phone. I've lost count on the friend's and family's cars that have been declared totaled over the phone. Once the adjusters found out how far up into the car the salt water had reached, that's all they needed to know. "Salt water and car electronics and mechanics don't mix" was the standard phrase. I'm sure someone will look at these cars before officially declaring them totaled though at least if the water intrusion sounds like it's borderline.

 

Been there with a Northstar Aurora. They finally figured out why it would stall (after my cousin used his GM email and contacts to get in touch with the head of GMs premium motor division) and she said she lost confidence in the car! Aargh!
something the OP has to keep in mind as he decides which road to take.