It's possible that the plane needs to get to MCO for a charter or something. As for the ground crew, at least British Airways operates a 777 from London-Gatwick already, so MCO is certainly no stranger to 777s.
As for selling J as F — usually, two-class birds will have J as Y for elites/full-fares, while two-class will have J as F. This must be a retrofitted 777, which means there's only two classes.