The same thing happened to my Dad's 94 YJ. Dropping the tank isn't that bad- just leave the straps that hold the tank to the skid intact. They are a PITA to get back on. It could be the gasket around the fuel pump or the lines coming from the pump going to the rail. My dad bought a length of gas hose at autozone pretty cheap and we replaced them both.
You'll need to disassemble the gas filler so those 2 hoses can slip between the frame and the body when you drop the tank. There are 4 nuts that you need to remove under your rear bumper (if you have one) and three nuts and bolts to remove where the skid meets the body under the tub. Then you put a floor jack under the skid and wiggle the whole thing around the tailpipe. It will take some prying and kicking to get it to move. Once it comes down low enough to get your hand in there you'll need to disconnect the wiring clip to the fuel pump and 2 vent hoses that should just pull off the nipple they are on.
Here is a pic of my dad's w/ the tank already dropped and a pic of what the tank looks like (minus the fuel pump) The four studs in the first pic hold the rear of the skid on. The muddy tube to the left is one of the vent tubes.
Just remember ... No smoking during this project!