I found that dropping the tank is a bigger PITA. And it's VERY heavy when full. I use the floor-jack to lift the tank's rear end while trying to forcibly jam it into place above the darn cross-member.
OTOH, my sweetie & I easily lifted the bed off, by hand. It's mostly me doing the lifting, she was mostly just for stability, cuz it's kinda bulky & awkward b/c of its size. Remove the heavy tailgate beforehand, and especially remove the mudflaps so you can set it down flat on the ground. Otherwise, you'll have to stand the bed up on its end.
Another clever alternative is hoist & prop up the bed w/o fully removing it. IOW, somebody here shifted his bed rear-ward by about 2', and then used wooden lumber to prop it up about a foot above the frame, giving access to tank.