I had a 280Z with a sunroof that I didn't like at all. I found a donor roof from someone local who was parting out their car and then got some quotes from two different shops to weld it in. Both shops wanted to cut the old roof off at the legs and then weld in the replacement. From what I understand, this is the proper way to do it. I can't remember how much I was quoted but it was high enough that it convinced me to do it myself. I took the donor roof and cut a piece that overlapped the sunroof hole by one inch all the way around. I took a bunch of measurements to insure I was cutting the metal from the same location on the donor to the corresponding location on the car. I had a friend spot-weld three one inch wide steel strips that ran the length of the roof to act as a stiffener. I then riveted the replacement panel into place at four points. The replacement panel got attached from the inside of the car. Then the fun began! With my son bracing the roof from the inside of the car with a block of aluminum, (poor mans heat sink) and gloves, I began to stitch-weld the roof in. In order to keep the heat down and prevent warping, I would weld a 1/2" to 3/4" bead and then stop and then go to the other side of the roof and repeat the process. We had to stop quite a few times and let the metal cool down because I was afraid of the metal oil canning. It took practically the whole day. After the welding was done, we ground the welds, did some tapping with some body hammers and then applied our body filler. Getting the roof straight with all the block sanding, guide coating, etc. took about two days total. When it was done I had the whole car painted and it turned out terrific. It took longer than I thought and was more work than I expected but we had fun. I was glad I didn't pay someone to do the job. I sold the car to a friend and see the car regularly and it looks just as good now as when we completed the job. Like all the work required on these cars, I like to do as much as I possibly can, especially since my son is usually involved. Besides, I think I do a better job than most suppliers would do anyway. Good luck with your efforts. Bruce