The first thing I did when I got my Jeep was replace the gas tank. The only advice I can give is that if you replace your hoses, make sure they are exactly the same length. This may sound obvious but especially the vent and filler tubes can be a massive pain to reinstall after the tank is bolted up. Good Luck.
I went ahead and bought a new steel tank, I figured the last one lasted a good 23 years and this one will last probably longer than that and longer than I have the Jeep so it's probably a good investment.
Currently Jeepless - Previously owned 1983 SJ, 1979 CJ-7 and 1991 YJ