Been There, Done That!!!
Yes Mark, that is exactly what you have to do.I have done it three times now. The little foam float on the sender contains a magnet and this goes rusty. This rust, in turn, reduces the diameter of the hole in the float and it binds on the stem on which it slides. Repaired this twice. Last time I was punching into a head sea all day with a half empty tank and the free surface effect of the water broke the stem of the sender clean off.I have been given cause to wonder why Hunters needed 56 screws (if I remember right) to gain access to the sender. Get an electric screwdriver and REMEMBER where the different lengths of screws all came from! The woodwork under the bunk is filleted down with silicone adhesive and this makes it difficult to know if some screws are still to be found. Also I think I chiselled away various bits of wood to make it easier next time.