I think you have enough input on price...and hopefully your local dealer will help you out on a trade..../ especially if that was where you bought them.
A couple of tips ....make sure the gun is pristinely clean and properly lubed when you take it in, to trade it. I can't tell you how many dirty guns I see come into my buddy's shop - looking for trades / and it affects what he will pay for the gun.
Make sure its not loaded...no rounds in the mag either....its just smarter ( and you'd be shocked to know how many times they are loaded).
Before you buy again, ideally you want to shoot a variety of 9mm's ..get a feel for the difference in the controls, grip angles, sights, how the triggers feel as they break, how far they travel ..how they reset, width, weight ....all of that stuff makes a huge difference.
There are so many 9mm's out there...poly frame, alloy frame , steel frames...it would be hard to suggest you look at anything ...but at least look at offerings from companies like Sig ....at least a 239 model (their single stack - relatively small gun) ....and some of their larger full size guns like a 226 ...and some kind of a 1911 in 9mm ( Springfield, Colt, Kimber, etc ) ...
and rent - or try and shoot as many as you can before you buy.