You shouldn't have any problems filling it in your truck. If you do, take your business to another station. Diesel is not going to flash like gasoline from static electricity so it is pretty safe to fill into an ungrounded tank.
There are lots of ways to get it off your truck 1) put a strap around it at the top ring and lift it out. 2) If you have the bungs in place, you can tip it over and roll it off using an ATV loading ramp or 2x12 piece of lumber, 3) you could put it on a pallet and strap it securely and use forks on your FEL to lift it. 4) build a frame around it as one member did so you can attach a chain to the top lift arm and take it out with the FEL.
Finally if you have a pocket full of money laying around, they do make an attachment for loading forks that is designed to lift barrels and it fastens and unfastens automatically. You just drive forward to position it around the barrel, lift and it closes, then to remove lower it a bit and back out.