well first off run as much gas out of the tank as possible.
try too spray some penetrating lubricant near the bolts.
and yes the fill tube is a bitch
if you have a tranny jack youll be way better off than most its easier to lower the tank as well as putting it back in its place.
as far as wiht the tank out, there is a ring that is usually rusted and hard to get off, spray a little pb blaster on it let it soak for a few, then come back and attempt it. you can get a tool for it, but a blunt flat punch, or screw driver.. and hammer will work fine. make sure when you are installing that the sock filter doesnt come off.
hpfiend, yeah the first time was a little long, then time after time it got easier, especially on batter condition foxes or foxes that had the tank previously dropped before. but after you do so many its like 2nd nature.