I did this mod last summer, it is pretty easy, you just have to have faith in yourself to do a good job, you only get one shot. I did use a needle and thread to sew up the corners by my own choice, I just wanted a cleaner install.
Here is a brief how-to:
1. Disconnect all electricals from underneath
2. Open tailgate and cover with a clean drop cloth
3. Remove seat and lay on the tailgate with the bottom facing the rear
4. Loosen the upholstry and peel it back to reveal the middle portion inner foam. When you get to any seams that will stay revealed, carefully cut the seam thread with a new razor blade. take care not to cut the material.
5. Use a very sharp 6" or longer straight blade knife and carefully cut the foam along the break line where you want the new edge of the driver's side bucket seat. Its not a straight cut either...It has to taper outward at the top edge of the seat.
6. Break out the sawz-all and commence to cutting. Try to get the cuts as close to the welds on the frame as possible. Mine was a tube frame, some I have seen were a flat pressed sheet frame. depends on the year I guess. You can salvage the arm rest at this point too if you had plans on using it like I did.
7. Pull the upholstry back over and trim as needed. You should end up with just one major seam that runs up and down (see pic) Use a heavy duty cottom poly thread and a heavy gauge needle. A pair of needle nose pliers doesnt hurt either to pull the needle thru the thicker material. Use straight pins to hold the seam together. Ya didnt know you were gonna have to be a Suzie Seamstress did ya?
8. I used zip ties to help hold the edge of the upholstry to the frame.
9. Work the wrinkles out as you sew. dont rush this part. Make several passes back and forth along the main seam to help keep it strong.