If it's not covered by warranty, it "may" be covered by your insurance. I say may because it depends. If something hit it and cracked it then it is covered. But if it cracked because of a construction defect it may not be covered. I'd give Winnebago a chance first to take a look and then try insurance if they can't, or won't, fix it.
Edit: If it is a 10 year old motorhome as the person above states, then Winnebago isn't covering the damage. Your best bet is insurance, but like I said, it depends on exactly how the crack got there.
