You've got a project for sure. If it has been thru 5 owners in 14years then it was poorly built to start and has gone downhill from there with 'improvements'. These shops put emphasis on 'curb appeal' and the mechanical issues will sort themselves out.
Good thing it is in your hands, i can tell you'll get it right.
Be careful about getting what you wish for removing the dash, i bet there'll be serious rigging behind there, out of sight. Have your camera ready when you do, ok?