As stated above, look for furniture that comes apart and each piece will fit through the door, then assemble the furniture inside the camper. We replaced the 2 original rocker chairs, the stand-alone kitchen table and 4 chairs for a household 3 seater recliner sofa. The main body of the couch "just" fit the door. Before purchasing, I measured the couch several times, and even had the furniture store remove the backs and I measured and remeasured everything. All 3 backs fit through the door with no problem, and after it was inside, I added 6 wheels under the frame so it could be moved easily inside the camper. The thing to look for is furniture that fits together in pieces or sections and then assembled inside.
Original:
Slide out emptied:
Couch:
And with wheels, we can move it facing the back window and television. This works absolutely wonderful for us: