If you no longer own or rent a home (no longer have home owners or renters insurance) you'll need a "full timer" policy that includes personal liability. Covers you for the stupid things we've all done now and then. You hit someone with a golf ball and they drop dead, that kind of stuff.
Many like to have full replacement cost coverage. We do, but it is a lot more expensive than "regular" coverage. Most policies will max out the payout at whatever your coach was worth, at retail, the day it was destroyed. Just a couple of years from having taken delivery this will be way short of what a new rig would cost you. Get out 5 years or more your settlement will relegate you to shopping for a similar aged rig or putting out tens of thousands additional for something newer. Any replacement cost policy I'm aware of will buy you a similar make/model rig of the model year in which your old coach was destroyed. If you buy new this year and your coach is lost in 2017, they'll pay to buy you a new 2017 rig. Typically after 5 years this will drop - they'll pay you 100% of whatever you paid for the rig new.
Your current auto insurance company will be happy to sell you basic coverage, but for the additional coverages I mention above you'll need to speak to someone that specializes in RV insurance. Progressive and GMAC are a couple of the bigger ones, but there are a number of other smaller companies too. No doubt others will let you know who they are with.
Whatever anyone else tells you would be a fair premium, take it with a grain of salt. There are too many variables for anyone else to be able to predict what your premium will be. Suffice it to say, you do need to do some homework. I'd shop at least four separate companies to be certain you were getting the best value. (Be aware, that many clubs and organizations will sell you a policy too, such as Good Sam, or FMCA, but those policies are actually underwritten by someone else, most likely GMAC).
Jay & Peggy Monroe with Dolly
Can't take it with you - don't plan on leaving any behind
2016 Newmar London Aire 4553, Spartan chassis
Wrangler Unlimited toad