I have a 29 as well, and own an upholstery shop, so I have had the entire interior of a 29 apart!
There is an easy way and a hard way...... well even the easy way isn't that easy!
You have to start by pulling the front bolsters out, then you can get access to ALL the through-bolts on the backsides of the gunnels. Unless you have really long arms to reach the frt bolts, you'll have to pull the bolsters. The through-bolts should be 10-32 with a 3/8" nut size. Once the gunnels are out, you can then pull the back seat.
I have tried to get the back seat out without doing the aforementioned, but since the hullsides taper narrower towards the back of the boat, you can't squeeze the backseat any farther backwards to get past the gunnels.
You may find the back seat woodwork kinda rotten. In that case, youll have to rebuild all of the woodwork and fibreglass it for reinforcement.
My shop can perform all this work, if you wanna ship it. I can send you some pics of finished 29 interiors that we have done
If you are handy (and flexible) , you should be able to do all this yourself