Some shops don't like the back windows from 92-99 because of the angle. When my car was done, they removed the rear seat, the seat back, and the rear deck for better access. He said he didn't HAVE to do it that way, but wanted to to make it right.
It makes it easier if they trim the tinting to the OUTSIDE of the rear window first, then apply it to the inside.
The rear defrost isn't a prob, either, depending on the type of tinting they use. Mine has no slits, and works great, with no damage to the tinting, and no shorting of the grid.
Just remember if you go with tint, you may want the halogen backup lamps that are 250% brighter so you can see behind you while backing. They really saved my butt, and I only went with 20% all the way around.