For surfing you will need a decent telephoto. At least a 600 mm. Add to that a 70-200 mm 2.8 for the snowboarding and pretty much anything else. I have a Canon 20D and it works fine for action shots. You don't NEED any camera body other than anything similar to the 20D for what you want to do. For surfing photography the lens is way more important than the body. I believe you can get all that with a $5,000 budget.
BTW Back when I was a broke surf rat I talked QF into letting me paint the outside of the shop in exchange for a new board. Ahhhh those were the days
