I can't speak to your trailer issues, but I would like to add to the fireplace discussion...
When we purchased our trailer, I thought the fireplace was kind of hokey. After using it for awhile, we have come to really like it! It adds useful heat (1800W) and a surprising amount of ambiance. I find myself mesmerized just sitting and watching - just like watching the coals of a real wood fire. This is especially useful if you are camped in a National Forest with fire restrictions in place. [The DW says I'm easily entertained].
Two points: 1) I had reason to remove ours for other work. It is about 4" thick but has quite a bit of space behind it. Is there a "heat/space" requirement for clearance around these things? You should research this issue. 2) It does require 110VAC to operate. So you will either need shore power or a running generator plus a 110V receptacle to use it. If you boondock, it would pull down your batteries quickly if run on an inverter.
Good luck making your decision and modifications.