Hi Adam, welcome to the Cameralabs forums!
(I'm gonna move this subject to the Buying a new camera section...)
In terms of quality, you can certainly make a big print from a 10 mpixel DSLR, but you may still want to 'acquire' a file from, say a 400D or a D80, either from a shop or a site like flickr and output it using the printer or service you had in mind to see how it looks.
As for lenses, Thomas is dead right - you'll need something in the region of 70-300 for most sports, and the faster it is the better. By fast I mean both in terms of aperture (smaller f numbers are better, but much more expensive) and also focusing (for Canon, get USM lenses, for Nikon get AF-S).
If the surfers are really distant though, you may need something even more powerful. This is where it can start getting pricey, although products like Sigma's 50-500mm
can give you a massive reach at a 'relatively' low price.
The budget option though would be to go for a twin lens kit, where you'd typically get an 18-55mm and a 70-300mm. Do make sure the longer lens has quick focusing though or you'll quickly get frustrated. The Olympus E-510 twin lens kit is also one to consider.