You should be able to knock out most of that. Buffing out the boat is mostly elbow grease. There are plenty of threads on here with lots of details. The rear seat can be done for not a lot of money as they were still pretty basic. Even cheaper if you can do the upholstery work your self. Spider cracks are can be done if you have some experience or are willing to learn as you go. Working with gelcoat isn't too tough. Sound to fit your budget might be a little basic, but you have options there. I might even know a guy who can get you a deal on wheels.
CUSTOM WHEEL & TIRE PACKAGES
$125 LED LIGHT PACKAGE - FREE SHIPPING
REBUILDING HOLLEY MARINE CARBS - $249 DELIVERED
REBUILT COMPLETE MARINE HOLLEY 4160 CARBS
FOR 302, 351 & 454 STARTING AT $425 DELIVERED
Email - firstname.lastname@example.org