As I am a Harley Technician, I can tell you that MOST HD dealers won't take your bike in on trade, with today's economy, they are having a hard time selling their bikes as it is. IF they were to take a Honda in on trade, they will only give you about 25% of what you could get for it by selling it outright.
As far as the Dyna goes, I can give you a little advice...EXCELLENT bike...I have an '04 FXDX Sport, I have kept the engine at 88", but have worked it up pretty good and I just got done Dyno Tunning last month at 108Hp and 111Ft/Lbs....not bad from a carbed 88 incher. The Dyna you are looking at has a 96" engine and fuel injection (HD's Oxygen Sensor Equipped Delphi Fuel Injection is hands down state-of-the-art fuel injection for motorcycles, no other manufacturer comes even close to HD's injection system). You most likely want a good sounding bike, right? When you buy the bike, have HD install the Screamin Eagle Hi-Flo Air Cleaner and Slip-On Mufflers AT THE TIME OF PURCHASE. If you do this, you will HAVE to have the ECM remapped for more fuel and better timing. At MINIMUM, have them install a Stage 1 download or BETTER yet, have them install the Screamin Eagle Super Tuner or a DynoJet Power Commander 5 with Wide-Band O2 Sensors, both the Super Tuner and the PC5 can be generically mapped but perform best when Dyno Tuned. Doing all this AT THE TIME OF PURCHASE BY THE DEALER, nothing can void your warranty, and it can be added on top of the cost of the bike loan.
Hope all this helped.
Happy ridin'!!!!
***NOTE***
DO NOT listen to FART from above, he is an anti-HD troll that will say anything and everything he can to put HD and their bike owners down.