G'day
@Dajotrad I installed a Planner brand diesel heater in our 17.58-3OB. I went for the 2kw version with tank, pipes and outlets. We have used it a fair bit so far on our holiday and I have to say along with others, best bit of coin I have spent. Wife and 2 daughters, you know happy wife, happy life...
Have used it every night and morning for probs 2+weeks and only used about 2-3 litres of diesel.
Biggest thing for me was cutting a hole in the floor of our brand new van. Bit of mucking around. Maybe 6 hours to install, with checking and double checking before cutting and making sure stuff will fit. Either gas or diesel, I think you will be happy, just personal choice. I went diesel, mainly for cost wise, but had spoken to some other people as well. For me, free camping running the fridge, the hot water and the cooking, then adding a heater to the equation just didn't work. Plus we had an experience of running out of gas in the middle of the night and the food in the freezer defrosting.