To determine a price, here's a list:
- eBay, but see if you can find bikes that have sold and the actual number they sold for
- Craigslist, especially the Craigslist local to you. You'll at least see what others are asking.
- Kelly Blue Book (kbb) and NADA price guides give you a ballpark number, but it's a pretty large ballpark. When buying or selling, I take these numbers with a grain of salt, but they can give you an idea.
- Check the sites mentioned above where people have suggested you sell, i.e. the BMW MOA Flea Market and IBMWR.ORG marketplace. While being a good place to sell your bike, these can also serve to give you an idea of what to ask for your own bike.
If you live in the northern climate where riding really doesn't happen during the winter months, then wait until spring to sell, because it will move faster and at a better price.
I've pretty much just restated here what everyone else has said, I just kind of put it together in a single post.
If you're experiencing health issues, (couldn't miss the Agent Orange comment) then I hope you get well soon, or remain as healthy as possible.