I sailed on a friend's Bene 311 this past summer. I don't remember much about the head, except that it was at the base of the companionway steps.
I replaced most of the black water hoses in my O'day 35 last spring. I suggest that this IS a project for cooler temps, as it keeps the "bouquet" to a minimum...
My boat was equipped with a VacuFlush head, which I have grown to love. It was plumbed with Dometic's flexible hose, which was not that great, nor was it worth what the P.O. paid.
I used 1½ schedule 80 (S80) PVC for any straight runs, and used Trident 102 (white) for anywhere that the hose needed to go through a bulkhead. To connect the S80 to the T102, I used off the shelf 1½ PVC connectors, PVC Primer, and PVC Cement from the local big box store.
The trick when connecting PVC pipe to flexible hose is to use off the shelf PVC fittings WITH (and this tid-bit is worth $$$) the Sealand 307341513 Custom Hose Adapter and double hose clamps.
This is a non-ribbed barb adapter which allows for 1½ PVC fittings to be used with 1½ flexible hose. These sell for about $3.50 each, and they are worth every cent.