First, it's great to ask questions from people that are in the KNOW! Or, at least should be in the know.
The 1500 will limit you on your payload, but length shouldn't really concern you as much because there's not a lot of difference between pulling a 26' or a 33' TT. Yes, there's a little more back there, but negligible difference.
I would definitely be looking for used since this is your first one. Look 3-4 years old, but one owner and appears to be taken care of. Before you decide fully, hire an RV tech to give it a once-over. It'll cost you a couple hundred $, but it will be worth it.
If you want a trailer with a bunk room, it will have to be over the 30' length. They make them that have the beds in the corner in less than 30', but not the extra room.
On Raleigh's Craigslist, I found a few. A couple are over your weight restriction, but....
https://raleigh.craigslist.org/rvs/d/2015-keystone-cougar-xlite/6469444462.html
https://raleigh.craigslist.org/rvs/d/2015-forest-river-wildwood/6466316439.html
https://raleigh.craigslist.org/rvs/d/2014-rockwood-by-forest-river/6442613316.html
