Julie, where are my manners, Welcome To The Forums. I hope your Christmas and New Years were enjoyable and not too cold.
Just a hint or two, a little information goes a long way in solving problems and a lot of information(nothing personal of course) will spark the creativity of these Cretans who forgot to welcome you. No offence meant guys. Giving the make, model and year of the item you are talking about helps and is normally the minimum info you must supply.
Also there are a few code words or short cuts used like; DH(darling husband), IIRC(if I remember correctly) and a lot more you will learn about.
There are also the infamous POLICE, Weight, Tire Pressure, Insurance and Liability not to mention the I'll never shop there again's. Everyone, well almost everyone, means well it's just that many of us are older, approaching puberty and highly excitable, so bear with us and enjoy the best location for all information RVing available.
I don't know how your aluminum rock guard is mounted but one way to ease the transfer of cold to the interior is to provide thermal break between the guard and the skin.
Not to be a smarta$$ but there are about 783 million things that would work to keep the guard from contact with the skin. If your guard is screwed on simply remove the guard and look for something flexible and cut it to size and screw the guard back on with slightly longer screws.
I doubt that the walls are hollow so the old blown in insolation is probably out, as is adding the insulation to the inside wall skin or over the guard. I can think of some more ways to solve the problem but most aren't pretty and moving to the So West desert is probably out of the question.
Opening a window or roof vent will help eliminate the condensation but that wall will still be cold and that means more hours on the heater.
Well my suggestions seems to be the easiest way out, create a thermal break.