Congrats on the new truck, I also picked up a 2019 back in October as I didn't want the 2020. If you happen to have the prep package you can simply order one for your truck and drop it in. Mine did not have the prep package and I reused my B&W patriot and put in new rails. Having rails in my truck doesn't bother me at all so it worked for me.
Consider doing it yourself. My dealer installed the rails on my last truck and I wasn't happy with their install so I installed the rails myself in the new one. So If you are doing rails and somewhat handy it's an easy install in terms of not complicated but there are tight areas so smaller the hands I think the better it is.
Etrailer is a excellent place to order parts, excellent service and also have excellent how to videos on just about every product they sell.
Dan
2019 Chevy crew LTZ 2500 HD Duramax
2017 Wildcat 29rlx fifth wheel