That looks like a job!
You can buy adhesive remover in a spray can at auto supply stores.
I believe it's made by 3M.
If you read the label, it states the main ingredient, which you can buy at a paint store. I bought both, the spray can is easier and does seem to work a little better.
It wont be an easy job. Our coach had 2 year old graphics on it, and it was tough.
You'll probably need to figure out how to cover it with a cloth so it can soak.
Do small areas, after soaking, rub with terry cloth rag soaked in remover.
In my case, a heat gun helped soften it up.
PS: Don't leave the used rags wadded up. Hang them to to dry before discarding. Petroleum products have a risk of spontaneous combustion!