I don't know if this will help......my TR3A seats are nothing like the TR6
seats, but they are similar to my '66 MGB (I'm pretty sure). It was a pretty
easy job.....I'm sure you can tackle it.
If the foams are crumbling ( the sag in the seat center), then I would buy new
foams. When you buy the diaphragm, you get a bunch of hooks. There are holes
in the seat frame and these hooks stretch the diaphragm between the frame. As
I recall, I put burlap material on top of the diaphragm. Then I added the foam
and the cover. The toughest part was lacing (sewing) the inner panel seam
through holes in the diaphragm.....I don't know if the TR needs this. This
lowered the inner panel to create leg and bottom support in the seat. After
this, the cover was secured to the seat rail with semi-circular spring
clips.....and......"viola", the bottom was done.
The back was even easier in that the foam rests on the frame. The "B" had a
foam front, a cardboard interleaf separator then a foam back. I put the
components on in the flat, then put the cover on like a pillowcase.....making
sure everything stayed in place until it was buttoned up.
I bought good quality leather covers and after 5 years they still look and
feel great........well worth the extra investment.
Good luck.....keep me posted.
66 MGB GHN 3L 78708
60 TR3A TS 76779 L
PS....Why pay good money to have someone else do a job that you can screw up
as well as they can.
An interior is extremely important......after all, you'll live in this part of
the car more than any other. If you're not completely happy with what you see
and feel around you as you're driving hither and yon, you'll be miserable and
want to rip it out and do it over.
Take your time, learn to be patient with your interior.....you won't regret
the extra time you took.