I replaced mine two years ago.  Best to flush and empty the tank as much as possible using the deck pump-out.  Regardless, there will be some unpleasant stuff.  Wear gloves and stuff gobs of paper towels under the fitting.

This is often the nastiest section of hose because as your tank fills up, the bad stuff climbs up this hose quite far and sits there.  Due to the large diameter of the host, there's a lot of surface area and therefore a lot of stink.  Sanitation hoses that have neoprene, EDPM, or butyl-rubber inner cores are the best choice here.  Avoid using the white vinyl/PVC hose with the built-in helix for this duty.

I wore an organic vapor respirator which helped considerably with the odor, wear gloves, put an open garbage bag with lots of rags under the connection to catch as much as possible from escaping.

A dock mate used a hole saw to drill a hole in top side of hose just past the barb exiting waste tank, then used a small wet/dry vacuum  to suck out remains before disconnecting hose.. He still had to clean up vacuum but nothing went into bilge.