Overall lenght question

You won't grow in length by the whole 6 feet due to the overhang but you will find truck swing room a bigger issue. Lot's of sites can handle the length once in but ditches, other trucks, trees, boulders, etc on the trucks left side will create serious issues.
If you camp at commercial campgrounds you will be OK, state and federal is a whole different issue. Especially older ones.

Fifth wheels pull better....but differently. They will cut sharper than a bumper pull because the attachment is more forward. Thus you can curb them or run in the ditch somewhat easier. Also they react slower to steering wheel movement when backing up. Just keep this in mind and you can adjust to a fiver very easily.

Yes, should fit in same spot, but like mentioned, might need more room to maneuver the truck. Another consideration...a 41' FW is going to be much taller than your TT, if height clearance comes into play.

Jerry

Length wise you will be approx the same as your current setup. Figure 6 feet over the truck bed.