The Ford V10 is pretty well bulletproof. You can go over any mountains that have roads up them, though it may not be the quickest vehicle on the road (but also not the slowest). You also should not have any trouble with it overheating, assuming there is nothing malfunctioning and no add-on in front to block the airflow.
Do be aware that the V10 is a high revving truck engine, so it will sound like it's about to self-destruct when you push it fairly hard and it's making power. It won't; but some people really don't like the noise, or think it betokens something horrible.
One reason that many people like to have a towed vehicle, besides the obvious utility if camping for an extended period of time at one place and touring around, is to have a sort of escape pod should anything break down with the motorhome. If you take care of the motorhome, it's not at all likely to be disabled in the middle of nowhere; but perhaps having another vehicle will ease your mind.