Our 1900s had no galley, just a coat rack behind the stub bulkhead on the FO side. IIRC the armrests and seat back came off the seat, the fore and aft limiting pins came out of the seat rails (the rear outboard one was a bastard), the seat's aft rail grips slid back and lifted out of the rail, then the seat slid off the forward end of the rail and lifted out.
We had some of the first airliner configured 1900s, including the prototype, UB1, N6667L. In fact the first editions of Beech's maintenance and operations manuals depicted 67L in our company livery. She had been a sales demonstrator and was the only one we had with an autopilot, a real POS not quite ready for prime time. We had to get an STC to disable and remove the AP, which was adopted by Beech and applied to new production, as airline customers were requesting their planes not have it, and it was part of the original type certificate. She would trim up so stable the autopilot was practically redundant.