If you do plan to reuse the panels be sure to mark them before removal. In your case with a MCI, I would lean toward using plywood instead. Gives a thermal break and an excellent surface to attach other stuff.
Mine is insulated with cut to fit foam sheet insulation. Takes some time but easy, safe, and effective. Select foam sheets that add up to the the required thickness. A few cans of low expansion foam gap sealer and you are in business. Many people fir out the space for even more insulation. My 4107 is short on overhead clearance so it is standard thickness.
Spray in foam is good too but not always available or affordable and must be done all at one time. Forget something, more of a problem that cut and fit.
A lot of planning needs to happen before the insulation. Wiring is a biggy. If possible plan an accessible wire run on each side of the coach to allow future service or mods. A floor plan taking into account window locations, skylights/vents, heating cooling, bathroom location to holding tanks ect. Lighting too. I am a big proponent of mocking up everything in cardboard first but then wife says I am short on imagination anyway.