It's best if you know how to do it yourself anyway. Order your own and show up with it. All you have to do is get it fairly close. You can fine tune it when you get it home. Honestly...all they're going to do is get it somewhat close anyway. As long as it looks mostly level and doesn't look like the nose of the truck is pointed up, just take it easy getting home and get a feel for how it's pulling (if it feels strange or sways, turn around and have them mess with it...better safe than sorry ) then pull out the instructions and start measuring. Expect to hitch / unhitch 2 - 4 times to get it the way you want but, after that, you rarely have to adjust anything.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition