Your gas tank is strapped inside the skid, the skid is bolted to the Jeep with carriage bolts.
If your bolts are rusted, chances are your metal tanks straps will be too.
The skid has to be dropped to get the tank out. You can cut off the carriage bolts, but you will have to buy new ones. Chances are you will have to buy new straps too.
What kind of skid did you get? If it's a Savvy Aluminum GTS, no worries. The Savvy tank skid comes with all new carriage bolts, new tank straps, and even new push pins for your fender liners.
If you bought another brand, good luck.