RG 179 type FSomething like this. Google RG 179 type F.
You may need a couple of new barrel connectors as well for the connections going through the base and I think one of the internal connections. Many folks have done this repair successfully but usually Winegard has said that is was repairable so I am not sure exactly what they think is wrong. You absolutely want to start by replacing the coax running down the arm first as it's a simple fix sometimes but you may already be beyond that based upon your post. Use some di-electric grease in all coax connections and it will prevent this kind of problem in the future if the fix works.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?