Having installed a fan in the empeg myself, it does dramatically help cooling. Mind you the only time I've had the thing shut down is from driving in colder weather and having the heating crancked up.
If you do want to install a fan, get the quietest one you can find! I've taken mine out because of the noise.
One day(tm) I'll get around to piping air conditioning up to the unit. I may just blow it only the bottom of the unit as that's where all the heat tends to come from.