Hi :wave:
The back box has rust as standard. I wouldn't worry too much as there's many layers which can peel off without there being any issue with function. Mine is 10 this month complete with rust on the outside but still working fine.
Have you searched the car for the lock for the wheel nuts? It might be hidden somewhere within the car or you could contact the last owner on the logbook to see if they still accidently have it. In 2005, spare wheels were still standard, so I'd ask about that. Ebay usually has spares or you could try scrapyards to source one.
So what colour and pics?