Advice for restoring Longines Water Ski Chronograph

I’ve just bought this 1968 Longines Water Ski Chronograph which is missing the inner bezel and the crystal and case are in pretty rough condition. It’s a watch I’ve wanted for some time and I would love to get it back in good shape. Would you send it to Longines or is there a better way to source the replacement parts and get the case tidied up and movement overhauled?