The best plave for you to sell it would be
http://www.rolexforums.com/
Join the site and you'll be able to post in the "For Sale" section.
Just know this, for
any online forum, potential buyers will want references. Most of the sales are done via bank-wire transfer and they want to make sure the person they are dealing with is not a rip-off artist (yes, there are still people out there trying to take advantage of the internet).
That being said, if you don't want to deal with a forum to sell your watch, you can definitely go to your local AD and see if they do take trades (not all do). My local AD does accept trades for all brands of watches, but they do not sell them. They literally have 3 or 4 places that buy used watches and they simply give them a call and ask for their best deal. TBH, I had a very good experience with this recently when I traded in a 2000 Polar Explorer II and a Panerai 111 when I purchased my GMT BLNR. I only lost a few hundred dollars vs. what I could have gotten selling them myself privately. Was it worth it? To me, yes.
I also see you're in Ventura, CA. Just Google "Used Watches" in your area and see what comes up. Contact them to see if they'd be interested in purchasing your watch outright.
BTW: Which Rolex will you be upgrading to?
I have four Rolexs at the moment. The brand new GMT BLNR, which is very hard to get yet. A white and a black face Daytona and a 2006 GMT Pepsi.