Having never owned a land-yacht, I am not best placed to give you advice on that part. However, quick google search comes up with a campsite at Lastva, just up the river from Trebinje. I have no experience of the campsite, but the area is pretty decent. River and a lake there and shade in the river canyon for a bit cooler sleep-stop. Campsites can really be hit and miss as I am sure you know. The locals are pretty lively and shout a lot, particularly when there's rakija involved.

So it really can be great on one and a nightmare on another night. Don't expect very high standard facilities, but you probably sussed that out already.
As you probably also gathered so far, the place is mainly about nature, with exception of a couple of towns, it is all mountains and rivers. So, Trebinje is not exactly going to be breathtaking, but it is a chill, walled, old town with some cracking wineries about; if that is your thing. Upmarket - Vukoje winery and restaurant. My fave, though, is a fair bit down-market - Tvrdos monastery, couple of miles down river from Trebinje. You can buy a 5L canister of good wine for 25KM (about a tenner) directly from the monks. At least you could a couple of years ago. The language may be a bit of a barrier, but you are more than likely to encounter someone visiting the monastery who speaks English. Anyways :"vino u refuzi" is the keyword and you get it from the wine cellar directly.. It is also nice enough, 9th century Orthodox Christian monastery to visit. Drink the wine quick, though, it is "young wine" and will turn to vinegar pretty quickly at 38C.

You can, of course buy bottled wine there too at much higher prices. Buying a plastic canister of wine from a monastery for peanuts is something to talk to your mates about when back home, tho' ..