Not familiar with the layout of the 420. Is there a designated spot for one and it perhaps has shelving or doors on it or no spot to put it at all? Would make a job simple if it has a place.
You’re probably aware, they’re available as stand alone units that are really nice but they take floor space which you may not have. Could be stored elsewhere in the warm months.
I loved my fireplace in our last rig and since we are on full shore power all the time, we used it for our primary heat last winter. So when we bought our 420 I was upset that it didnt come with one.
In Dec 2021, we added a freestanding, quartz fireplace (by ComfortGlow) that comes on casters so we can move it as need be. It'll be put in storage during the warmer months. We also use space heaters for the garage since the furnace doesn't heat that room. It doesn't heat everything, but keeps the chill off and has a nice aesthetic..