see above
a 2wd trans cannot be easily converted to 4wd.
the rear driveshaft would also be a different length.
you'd need the entire 4wd drivetrain to convert a 2wd to 4wd.
as to if you're better off, that's your decision, if it's clean it may be worth a body swap, but that's all subjective.
just know that if you buy a 2wd jeep you'll need another transmission to make it 4wd.