Well, if you are SURE it's the sending unit, be aware that many times it's a grounding issue. After I pulled mine out, I did the check with a multimeter per the FSM , and it was fine. I had cleaned the ground strap, but that turned out to be the problem . I rigged a test wire with alligator clips, and the sender was OK.
If you are NOT pulling the fuel tank, I would invest in one of those $8 lock ring tools. On an E-Body, you don't have a great deal of room to swing the hammer onto the brass drift you will need if you don't get the lock ring tool. The tank has a "ledge" just above the leaf spring.
Get a fire extinguisher, if you don't already have one. Hate to be obvious, but stuff happens.The FSM advises to drain the tank, but I would think an empty/almost empty tank might have more fumes ?
The rubber tank gaskets they sell aftermarket do not fit exactly right (they have a smaller inside dimension), but do work if you can get the tangs on the fuel sender into the slots in the tank opening. If I had to do the job again, I would try and ask if the dealer still can get them.
Good luck.