I had this done on my last coach (and it wasn't in a slide). Replaced the J-sofa, that was trendy at the time with a recliner. Just storage underneath so easy access to the bolts that held down the sofa and easy to put in new bolts to hold down the recliner. You may end up with some inconvenient holes in the floor and I lost a couple of "seat belt" seats. I actually did this mod twice, the first time with a sort of standard RV recliner and the second time with a compact residential model.
If your sofa is in a slide, it's either bolted into or thru the floor and should be easy to remove. They kind of disassemble so should be able to get the old one out the door. As someone mentioned, new recliners tend to come in two pieces (back and base) that snap together. Both pieces should fit thru the door.
This shouldn't be a greatly difficult mod.
Cheers,
tfw