Hi and welcome to the forum. For a first timer, that's a pretty hefty size trailer. Since I know it's coming, I'll ask.....what are you towing it with and what are the specs for your specific vehicle. With that GVWR, you should have a capacity around 10,500#+. You'll also need to know your hitch weight, since that question will be right up near the top of the list. And this is an important part....don't believe anything the salesman tells you....research it and confirm it yourself or get help here before making the leap. "Sure, you can tow that no problem" is the #1 comment that's likely not quite true. Remember, his job is to sell you a trailer, then it's your problem. So triple check everything.
KZ makes a good trailer. My cousin and hubby had a rear slide model for about 10 years and no issues, other than routine maintentence. It's a mid-range line, like most, and I don't recall any major complaints re quality or service issues. One thing that has been discussed recently and you might want to check is the roominess of the bathroom. Some have found that it's too snug to be comfortable and that changing clothes is very difficult. In my cousin's KZ, their bathroom door opened inward and it was pretty tricky to get inside, maneuver around the commode and manage to close the door. Just something to check.
Happy camping!