Tax, title and licence can vary by state. The dealer should be able to tell you that. Ask about other fees as well. I had one dealer try to pass off a $500 "Processing Fee" onto the documents.
Another thing, you will likely need a brake controller, Weight Distribution Hitch, Sway control, etc. My RV Dealer won't let RV's drive off the lot unless the vehicle towing them has them. If you don't have these things, most RV dealers will sell them to you and even install them... at a HUGE mark-up most likely. So find out about that stuff.
Go over in detail what guarantees and warranties the trailer will come with, and whether they are manufacturer or dealer based. One thing I love about the dealer I normally go through is they are very good about being completely upfront with everything. I bought an older used unit and I got a list of things they inspected and would cover in detail (and for how long), and they didn't try to sugar coat what wasn't inspected and was not covered. It was laid out in black and white. Which I was happier having that kind of detail rather than for someone to try to pull one over on me.
There will also be additional warranties and service plans that they will try to sell you. That is up to you whether you think they are worth it or not. But be aware it will be a decision you will have to make, so you might want to research on them ahead of time.