What you can actually expect at trade-in is low-wholesale for your rig, probably 55-65% of the NADA retail. NOT including any of the "option" items you added - you probably won't get a penny extra for them. But if you do not pre-negotiate the purchase price without a trade-in, the "trade-in" offer you receive will likely include a discount from the MSRP of the rig you buy, which will inflate the trade-in value to a more acceptable sounding figure.
Go to your local library and ask if they have the NADA Wholesale book for Rvs - many library systems subscribe to the NADA "dealer" or "wholesale" books. Then you can find what your 2003 is really worth. Credit unions usually have them too and will show the data to their members. I would target getting a 20-25% discount from the MSRP on the new one and receiving NADA wholesale for my trade-in. Some dealers will deal at that figure but others will not. You have to decide if the bottom line price is fair, taking into consideration the dealers reputation, location, after sale service, and whatever else is important to you.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL