I've used this Scotchbrite decal remover on two different RV's. It works great and also removes most of the glue. I used Goof Off to remove remaining glue.
https://www.amazon.com/Scotch-Brite-.../dp/B00EW7MUQ4
Then buff and polish like h2ojocky suggested. Note that "ghosting" from your original graphics will be very visible. I did my best to get rid if them by wet sanding, and then polishing to get gloss finish back. Some ghosting is still visible 4 years later.
I purchased my new graphics on Ebay from seller db_graphix. Just search "rv graphics". They actually had Montana graphics very similar to my original ones.
After 4+ years, front decal has faded and needs replacing again.
It took me 2+ days to remove old graphics, 3+ days to remove ghosting and polish, and 3+ days to apply new graphics. It was a real PITA.