Good news - my car is a black GM, and it was in worse state than that when I got it. Back when I had more time on my hands, I got it (and kept it) perfect.
Bad news - it is going to take a long time to perfect that. Think about paying a pro with a rotary to knock it out - it will take you 20+ hours. Getting the deeper marring out will probably take 2+ passes with a heavy PC-friendly leveler on an orange or yellow pad. You'll then need a medium polish to remove the hazing, and a final polish to get it looking great.
Or, if you want to get a feel for the PC, wash and clay it yourself, and pay someone to compound it only. This will cost you a lot less than a full detail, and remove the deep swirls while leaving buffer marks and light surface swirling. You can then remove that easily with your PC and Menzerna P0106FF or similar (a rotary breaks down compounds much more effectively than a PC).