Caution :-
If you look at the front seam of the tank, it should be as thick as the side seams... But if the seam is rusted ie expanded, then when you release the 6 bolts holding the tank up, then you could start a leak from the seam that will render the tank U/S.
If the seam is ok then you need to lift bit of carpet in boot to expose the inspection cover plate, remove this to allow you to get to connector and two fuel lines.
Remove plastic cover under offside rear wheel arch to get to filler pipe, release this.
If tank is empty, it can be lowered on a trolley jack, or if you have plenty of tummy, lower it down.
Not a big job, but bolts can shear. You will have rust around the outside of the filler pipe too, and you might need replacement jubilee clips.
Good luck