I did the tank on my Cosworth with the Renu process: http://www.gastankrenu.com/
It's been 3 years so far and no problems.
As for the sender, I haven't seen them around. Some have used one from a Fiero, you may want to search the site on that. If you're feeling adventurous, you could probably clean and/or replace just the potentiometer part of the unit, as it's a standard 90 ohm GM piece.