I just changed mine. 70 gallon tank, about half full. I had a spot in the yard where I could put the coach so there was a bit of extra room under the tail and put it up on the jacks. Which only added a little.
Threw a square of plywood down an put my motorcycle jack under. Also laid a piece of 2x12" board on the motorcycle jack. Hardest part was getting the filler hose and vent hoses off. Tank came down easy and tilted over to the passenger side as it came so I didn't even drop it all the way.
Somebody had been there before me and pinched the wiring a bit. I noticed I could loop the wiring out in front of the tank a bit so if I ever needed to test in the future I could reach it. And I did. Went back up and together and easier than it came down. But the coach wouldn't start. Now that I could assess the wiring I could see that it had power.
Down the tank came again. Filler and vent hoses a LOT easier the second time. But the tank didn't tilt nicely this time. Wobbled and flopped front to rear. Difficult for one person but it came down. One of the wire attaching clips had come off. Slipped right on normally but I could touch it and it fell off again. Crimped it, installed, and before I put the tank back up confirmed the coach was back up and running.
Bad part is that I'll be doing this again one day. The tank is old and hast some rust in it that it clogging the fuel pulp "sock" filter. I looked but couldn't find a bigger and better filter I could fit to it. (Yet) What it has is just too small and will be clogged up sometime I am sure.
This is the style of jack I have though mine came from WalMart and was just a smidge cheaper.