There is so much to photograph >that I would hate to resort to my P&S, but I wonder if I'm >risking too much taking the D7000 into the sand. > >Thanks in advance for any advice.
Cameras are meant to be used. So, go for it! Without a tailor-made 3rd party bag, you could use a zip-lock bag, with a section cut out for the front lens element. Strong rubber bands could hold the bag flush to the lens.
I don't think I'd change lenses on-site. If it's hot/sunny out (?) I'd be careful about letting the camera sit in the sun.
Lastly, it's possible to have a rider added to homeowners/renters insurance, for loss or damage, even in normal use. I have one that's worked fine for me when I've needed it. Takes the worry away.