Get new insulation. You don't have to us the same type as you removed. Sounds like you have the skills to do all the labor yourself. New "moho"s are priced out of this world. Your 34 footer would be at start at $125k and go up with any extras like a spare tire!(-: The low mileage is good, but you will end up putting in some $$ into the engine, stuff like cat converters, sensors, belts and hoses things like that. So, if over the next 2 years you spend $10k in materials and have a nice custom coach vs $150k bank loan and payment. Hmmmm let's see $600 per month loan payment for 24 months is $14k, so you will be ahead by $4k at the end of 2 years. I've done 3 of these projects over the last 40 years. The trick is to not "cheap out" the materials that you replace and try to take short cuts.
Rubber roof, yes replace it, but if you can afford it, then replace it with a single piece aluminum roof. It is easier than it sounds. The hardest part is getting the aluminum up on top of the coach and remembering to put on sunscreen while you are installing it. I always coat my roofs with white roof coating to reflect the suns rays.
You will have build any replacement cabinets, I can show you how to make the doors. Make cabinet bases the same way as the ones you pulled out. Buy an air nailer, titebond 3, and a bunch of clamps. I like 22 or 23 gauge nailers as they don't show, but an 18 will work just fine. You can use paneling or MDF and paint it. Many choices...... Wife and I prefer greys, blacks and reds vs the yellows and greens of many of the older coach styles. So, we remodeled... If you have questions or would like some pix private message me.