Mate I've seen a 100 times worse than that !.....Looks good considering it's been used as a daily for god knows how long !

I've got a really good wire wheel and a variable speed grinder you can borrow....Just buzz off any surface rust you find (be prepared though, it could turn into a hole )
then give it a good coat of primer + paint with rattle cans...then I'd lash on a load of wax oil just to be sure !

check your door seal mate, could possibly be leaking through there....honestly though, it looks alrite !...its been played with a bit before but nowt that isnt an easy fix !