I fixed myself, after getting a quote for $350, and I had to remove the tank, which I understand involves partially removing the rearend.
I had a rust hole at the bottom, and after a few failed attempts I recalled I had just purchased a new tank for another car and they offered a block off plate and gasket for the sending unit.
I ordered up the plate, neoprene gasket, bolts with o-rings, and the tapped bolt ring.
All for a Tanksinc tank.
Cut the rust hole out, drilled holes for the bolts, slipped the ring inside, it's not a full circle so it will fit inside a smaller hole.
Put the gasket on, and bolted the plate on.
That was a few years ago, not even a drop has leaked out, no seeping, nothing.