Like others have said check under the dinette and make sure nothing but flat floor is under it. Mine was that way, took out the dinette and put in two La-Z-Boy recliners. Dick
Before we got our B+ we looked at a couple that had pulled the dinette and put a table and chair in. Made the think look like junk IMO. We have a curved dinette in our B+ and would rather have the standard dinette and yes it can be pulled and replaced with one. I looked at ours and where it curves it just thin plywood bent to a curve so would need to have new cushions made. Yes the dinette can be pulled and replaced with a couch and really should not cost a lot but more than likely would. Just be prepared to put new carpet in as most are on bare wood/vinyl. But do you really want to eat on a couch vs a table or are you think about a add a table in front of the couch. We looked at a unit and that was what they had for a dinette arrangement. Forget the brand but it was one of more expensive ones, wife did not like it at all!
Depends...some booths, as in my motorhome, have storage under the seats which have access from the inside, as well as the outside of the motorhome. Also, some motorhomes may have electrical components under the seats. Just some things to consider...