Run, don't walk, and get Don Casey's Complete Illustrated Sailboat Maintenance Manual. West Marine has it by order, but you can do better at amazon. $60 at WM. It's actually six books in one, with the first book being, "Inspecting the Aging Sailboat." Right up your alley.
At $4000 I would be very curious as to what would make this a walk away situation, other than alot of work. You could probably sawzall the boat in two, yank out the motor, and still make money on the deal! Casey's book will tell you what to look for-and how to fix it, if possible.