Thomas, you wrote: "'Tom Hoskinson' - you suggested that all I need to do is to wash out the agent. Does that mean that HCA is a bad thing that will limit the archival qualities of the film, or does it simply mean that I have an easy job ahead of me washing that out instead of washing all of the fixer out?"
HCA is not a bad thing. As Jorge said, HCA is primarily sodium sulfite and water. Fixing and washing film and RC paper is different from fixing and washing fiber paper.
It is more difficult to get residual fixer out of fiber based paper than film or RC paper. And, in general, the longer the fiber based paper soaks in the fixer, the more fixer will be absorbed by the fiber base and the more washing it will require.
If you use non-hardening fixer, film is easy to wash since the thiosulfate (fixer) is primarily in and on the emulsion and on the back surface of the film base. The first water rinse removes virtually all of the fixer on the surface and about half of the fixer in the emulsion. Removal of the fixer (or fixer complexed with HCA) from the emulsion is primarily a chemical diffusion process. Each subsequent water soak and change removes about half of the remaining fixer (or fixer/HCA combination). You will fairly quickly reach a point of diminishing returns with the washing process - this is the basis of the Ilford minimum wash procedure.
No matter how much you wash, you can't get to a fixer residual of zero - and it isn't necessary. The safest thing to do is do a residual fixer check after washing. See The Darkroom Cookbook, pages 179 - 181. Kodak HT-1a is a good test and there are other good ones.
To remove the antihalation die, you could use Sandy Kings procedure of dissolving one tablespoon of sodium carbonate in a liter of water. Use this solution to pre-soak the film for 5 minutes, followed by a water rinse. Then develop the film. Any residual die will be removed by the fixer.