Hi Tony, it is not complicated at all mate and the advice I would give is not to go out and spend a fortune on an expensive system. You can make an excellent system yourself, all you need is an ro unit which you can purchase from ro man or similar, an ro200 is perfectly adequate if you are working on your own. You will need a holding tank, 600 ltrs is probably big enough if you are on your own, you then need a baffled tank for your van, check the payload on your van to see what size tank you are able to fit, but 400 ltrs or more is ideal if your van can take it. Get the tank secuarly fitted as if its not it could be very nasty in an accident! you then need a pump, a hose reel and a pole, you then have a cheap but very effective system, there is a link on here somewhere for a diy site that will show you exactly how to do it.
I started out with trolley, but I would say don't bother as it is a real pain getting it in and out of your van all the time and time consuming. If you are just using it for tops, I think that a backpack may well be a good idea although I have not tried one yet, I am planning to get one soon. Back packs are cheap, and probably an excellent way to try out wfp and make your own mind up as to whether its for you or not.