I don't know how much installation is, but its a LOT of work...will be very time consuming....
Good points, but I think this makes the job sound a bit bigger than it really is......we used the GM 32v feeds to power a converter for the units we found on a deal. The units were mounted near the old GM pumps, so power was there. The GM's draw much more amperage than the VF's, so even with conversion losses, there's plenty of power. No new breakers, and minimal wiring.
Hoses needed to be done, well, because it was time. Otherwise, the original hoses and thru-hulls would have worked fine without modification. We took the opportunity to completely eliminate the overboard discharge....flushing a pint (plus the human contribution) at a time, there is no reason not to just go directly to the tank.
Fresh water can be tapped from a nearby faucet or shower. Not a long run as every head has both a sink and shower nearby.
There are a couple of ways the units come "packaged". We ended up with two that integrated the vacuum tank and pump into a single unit. It's a setup that was designed for easy OEM installation. Screw it down somewhere, hook up the input and output hoses, feed it DC, and you're done.
For tighter installations, Misty is one, there is a bullet shaped vacuum tank hosed to the toilet, which is in turn hosed to the pump, and then to the waste tank run. A bit more complex, but designed for maximum flexibility for tight spaces.
There is definitely work involved, but it's not necessarily a complete refit, and it's not very complex.