I am also hearing good things about Criterion barrels. I think I saw some in stock at Joe Bob Outdoors or Primary Arms.
YouTube is full of how to do it AR barrel installing methods.
The 6.5 Grendel is a wonderful deer, pig and coyote weapon. If you need a follow up shot it can be very quick because of the low recoil. With the accuracy of a good set up you most often don't need a follow up shot because those hunting style bullets like 120 BT, Pro Hunter, Gold Dot, 129 LRAccubond etc. retain their velocity and terminal effect is awesome. I do suggest that you also get a brass catcher to mount on your AR. Also a great scope I have found is the Primary Arms 1-8x24 with the ACSS reticle. They also make a 1-6x24 that is less expensive but I like the 8 power for longer shots. They have Illuminated reticle that can be turned down on #1 or 2 and see them and it does not wash out your intended target at low light. Glass is really clear and they have a BDC in the reticle that really works. I have both the 1-6X24 add 1-8x24. I would also suggest that you get a linear muzzle device. The AR Stoner from Midway USA is fine and only runs $30 right now. This device does cut down on recoil a little bit like a brake but most important it directs the muzzle blast down range away from you and does not concuss the shooter or anyone beside or behind the shooter, especially in a shooting house or tent blind. I have them on all my ARs.
As for magazines again the AR Stoner a good to go. I am pretty sure they are actually made by ASC because they look exactly the same. Elander mags are top notch and top price but one thing to be aware of is you can load the cartridge OAL longer with the Stoner mag than the Elander.
Also when it comes to loading dies I have both the Lee and the Hornady. Get the Hornady. The Lee over sizes the neck and then expands it out and the necks crack on the case after a few firings. The Hornady is much better. If you want to crimp your bullets do get a Lee Factory Crimp die. It works with any bullet. With proper neck tension you don't need to crimp. IMR 8208, ARcomp, H335, H4895 are all great powders.