Just in case anyone else needs/wants to do this:
For the umpteenth time, liquid was appearing in the bilge.  Over the four years we have owned Rigel, we had solved leaks from the rudder post (very slow, intermittent, subtle), galley foot pump, stern shower, head shower sump reverse siphoning (Bad duckbill) and the hot water heater.  This time, I traced the leak to the holding tank, and verified it by putting red food coloring in the head.  Soon, the paper towel under the holding tank exhaust turned red.
I considered attempting to tighten the clamps, rebed the 1.5" hose barb...but we're talking original holding tank...and we were aboard...and I was due back at work.  So, we pumped out, purged with vinegar, pumped out, and left a diaper under the leaking hose barb.  
Ronco Plastics, Tustin, CA knows your Catalina Tank. 
Given the nominal cost of the tank, two hose barbs and sanitation hose, and the fact the that old, original hoses were a bit smelly, the crew voted for replacement. When we got back to the boat, the parts were there, and the actual replacement was fairly trivial.
I used the Dremel to reach in and cut the old hose (texture of cement) off the old tank's hose barbs.
Although the tank was empty, we positioned a few diapers and paper towels under the exhaust barb before I removed it.  Very little liquid, but a solid odor, as was expected.  The crew's instruction was to "Get that thing out of here."
We had a large plastic bag to put the tank in as I lifted it out of its place under the settee.  That contained a tiny bit of liquid that sloshed out as I carried the tank off the boat.  A local landfill/recycling station took the tank and hose.
Removing the old hose from the intake (head) side was easy, but I had to work a bit to get a short length off the macerator.  Unscrewing the macerator from its mounting made it easier. I left the hose to the pump-out in place, as it doesn't smell, but it would not be hard to replace.
I used the Raritan Saniflex 1.5" hose (Shop for it...wide variance in price), which was easily snaked into place.
I hope I'm running out of places that leak into the bilge, beyond a bit of rainwater down the mast and airconditioning condensate.
Regards, Jim