Yes, you did very well!
Filler pipe is most likely the cause of your fuel leak. Does it only leak when you fill the tank up? if so, put only 3/4 of a tank in

I had a similar problem on my 91 GT
brake lines and fuel lines can be replaced, should not be much trouble / labour.
Your car is worth ~ 3000 cdn, the repairs should cost you no more than 500.
As for the wheel wells, yes they often times to rust, especially here in canada! fenders can be replaced cheaply from a junk yard, or if its only surface rust, sand and repaint.
try to treat rust as you see it forming, its like a cancer that spreads quickly, I know from experience