Congrats on your purchase, I have the same rifle.
I've shot mine out to 1100 yds and it's a beast. I've been reloading my own rounds with Hornady ELD match 285gr with 88.1gr of Retumbo powder and match grade primers. I reload Hornady and S&B casings as well as load new Lapua casings.
I had to purchase a separate press (Lee Classic Cast) just to reload the 338 LM since it's too large for the progressive press to handle.
With regards to a bubble level, I'd highly recommend getting a SendIt electronic level. They are expensive but well worth it if you plan on doing LRP shooting. They are normally mounted horizontally, but if you purchase a separate mounting kit, you can put it vertical; it reads the cant setup both ways.
I personally wasn't a fan of the factory furniture, so I replaced them with a Magpul PRS Gen3 stock and AO Penguin grip. I also replaced the factory brake with an Area 419 hellfire brake. The factory brake is odd with where they decided to put the ports and it isn't optimal for recoil control.
Here's mine.