now what

Take it to a machine shop and it have "cleaned". They will blast and jet wash it at the very least when they see it..
Then just oil the inside and paint the out and run it.
I'd be more concerned that it leaked by the looks of the welds...
Maybe fill it and let it sit a day or so..

I'm not sold on 450 dollar pans these days, but only because i own 2 milodons and a couple baffled stockers.