I've sold a number of machines including a Viking 1+ and several old Singers. And I'm getting ready to sell my Viking D1.

My suggestions: First go to ebay and do a search for Viking Scandanavia 200. Look at the completed auctions to see what they have been going for. Although Viking machines do hold value, you are not going to get what you paid for it so expect to take a loss. Once you have an idea of it's worth, you could try listing it locally on Craigslist, or on the Sewit's Yahoo group. If you have any experience selling on ebay, you can list it there. You would need to think about shipping (how to pack, what it will cost, etc).

Have you discussed a trade in with the dealer you are considering? What are you looking to upgrade to?