The majority of Manatees have the vent hose going vertical and through a teak board enclosure in the port fwd corner of the stateroom closet. It’s a 3/4 ID hose leading to an exterior vent, usually on the stripe area. The enclosure can be opened by the removal of philips head screws. For future reference, an in-line odor filter does fit inside the enclosure. Removal of the vent hose from the top of the holding tank is nearly impossible with an athwart-ships mounted genset in fron of it, but you can still replace the reach-able hose inside the closet, install a filter, or even a fan to facilitate ventilation to the tank.
Replacing the pumpout hose requires disconnecting either end, most preferably the pump out side by unscrewing the pumpout fitting and prying the fitting out of the cap rail to expose the hose clamps. If there is not enough hose to pull it up far enough, disconnect the tank end and pull the whole hose out through the cap rail opening. Tie a strong cord to the end of the new hose and snake the rope through the cap rail and as much of the hose as your able to, then while some pushes from above, look for and snag the rope with a stick and hook from the machinery space below the galley. While someone feeds the hose from above, pull the needed length to the tank. Leave a little extra length on the new hose to make it easier to remove the next time. Keep a drill and file handy to carve out a bit of clearance in case the hole at the cap rail is too tight to get the hose clamp through.
Been there done that Larry. I also put in a new pumpout fitting on my cap rail to be able to use the marina mandated pumpout quick connect fitting. The OE treads are metric. I had to enlarge the hole to get the hose clamps to clear so I made a teak collar to cover the hole. 
