tractor won't start after 2 hour use. ?

Definitely sounds like the alternator is faulty, assuming no wiring has come adrift. Not usually hard to replace, depends on its location.
Fuel leak - from where? Check all unions are tight, replace copper or fibre washers if necessary, check fuel filter/bowl is secure and that any metal pipe has not cracked (due to vibration) or plastic pipe has not been in contact with hot part or chafed. Metal pipes often crack right at the union fitting.

Mr. Toad
July 2008