We have a big family do in Montana this summer and are flying in to LA. We would like to drive up from LA but I would like to know whether you think it is sheer craziness to try and drive that distance in three days (considering I will be the only driver) and whether we should consider finding an internal flight closer in.
Three days is almost a leisurely pace as long as you don't stop and wander too much enroute.

I am also a bit worried about driving across the desert as us Europeans are not very used to big open spaces, or deserts, and I would like to know what your advice is on this
Depending upon the route -- there isn't that much desert between LA and Montana. I am doing a similar route in about a month.

Mark