Fabulous advice here but I might add a suggestion to see what is on the used market. Lots of long-range guys where I live build a new rifle every few months and the old ones end up sitting around or getting sold. It would cost half as much and leave you plenty of room for a reloading setup, fantastic optics, a suppressor, or whatever your heart dreams of.
I picked up a 15 year-old custom rem 700 a few weeks ago and my first loads are already consistently inside of 0.300" at 100 yards. I got it for less than I've spent on some factory guns. Barrel almost shot-out? Who cares? There's plenty of budget left to rebarrel & rechamber.
Guys that make them often have leads on really great used guns for sale.
.300 Win Mag is an excellent choice, but to really maximize the potential of any rifle. handloads are a huge piece of the equation.
Great advice. I'd have to do the load development to optimize the gun like you said at least until I can learn the reloading part. Thanks.