You should be able to order the trim and everything you need, including the fireplace, from Winnebago. They are very good about that.
I was looking at a Tour that didn't have one either and was going to add one in (about $1100 for parts).
I've had fireplaces in RVs for years - some issues have occurred when the factory doesn't tighten the wires well at the terminals, and expansion contraction starts them to arc, and some have done some nasty damage to the terminal block. Generally it can be smelled before it turns into a real fire, but the main thing is just make sure the terminals are tight when you install.
