I have a NL 8'11 camper that I purchased used and all I did as mentioned above was a Bill of Sale containing names of seller, buyer, date of purchase, camper serial numbers, etc. Insurance company diffidently want to see this.
What I highly recommend is to get the new to you camper propane re certified at a reliable RV or propane outlet.About $250 charge if I remember. Mostly the cost of the new decal from the Government.
There is a reason I highly suggest this. Are you absolutely sure you are not going to insure it? Nothing is insured on the carrying vehicle and liability is an issue. House hold insurance for contents is only covered.Looks like a great camper that is as you know almost irreplaceable and for around $350 you are covered.