I think it was 03 when Fleetwood stopped making slide in truck campers. So zero factory support. Has no value in my opinion, especially camper that old & looking used. There are many brand 'orphaned' campers. Only thing brand specific would be the structure itself.
In '01 fleetwood offered 4 TC lines, the Angler, Elkhorn LE, Elkhorn and Caribou. Angler was entry level-wood framed, metal sided, the Elkhorn LE was also wood framed/metal sided but had the amenities of the Elkhorn. Elkhorn & Caribou were very similar in construction with more & higher end amenities offered on the Caribou. Both al framed, filon sided but the Caribou also had aluminum roof trusses and an ABS front nose cap where the Elkhorn used wood in roof/filon nose.
As to the length of nose verses cab length, there isn't any interaction between the 2-other than it does stick way out there an extended cab doesn't change how camper nose hangs. No reason to limit yourself to an east/west bed.
I have no clue as to resale value on older campers-if everything works, structure sound, its in your budget and you like it? Inside pics of the one you linked looks like new inside-so Id focus looking for signs of water damage-outside delam, jack mounts etc if you look at it. Actually with any used unit-easy to get swayed by what, if taken care of, doesn't age (or matter).
Just a side note-that particular Elkhorn unit, bed length, non slide , 1000#+ lighter unit, (an 8R?) is the one I was going to buy but 'we' ended up with our 9u. No regrets. I'm thinking I would be more like in the 6thou range. If I were to replace ours Id be all over that one just because I'm familiar with the product. but it is 13 years old.