71 GTO hoods are very hard to find, I would spend the money if you don't feel comfortable repairing it yourself to take to a knowledgeable restoration shop to get repaired. Notice I didn't say body shop. Don't take it to a shop that does insurance repairs on late models, use a shop familiar with classic restoration.
Look for a shop that will take into account the originality of your car, you want to preserve as much as possible and not just start throwing incorrect reproduction parts at it.
Oh, and Welcome! And post some more pics
Forgot to add......check the hood in front of the hinges...you might find some cracks in the inner structure. This happens because the hinges get stiff and pushing the hood down from a full open position puts a lot of stress in this area. From what I can see that hood is very fixable if there is not rust on the inner structure.
Also, gotta add, love the hubcaps. What a cool car, your mother in law had good taste for sure.
Painted roof is pretty rare too, have you gotten the PHS on this car yet? Did your mother in law save the original paperwork for the car? Protecto-plate?