Where is the radiator support arm? Mine is rusting and I intend to shape it up.

It would be supporting the radiator.

First, is it the top support or the bottom support? The top is just held on with four screws and comes off easily.. Take it off and spray paint the thing.. Cost is $4.60 for rattle-can.. Bottom has four screws holding it to frame, but also fascia also connects there too. Same thing.. take off and spray it down.. If you are not wanting to do it yourself, expect an hour to 2 hours labor plus spray materials. they will blast it first with prime and paint. Look at maybe $200 or so would be my guess.. they will milk it for all its worth from you.