How tight is the match chamber?
I ask this as you might not be able to shoot some ammo unless you turn the necks on the brass. That means that you'll need to start reloading.
The Griz is a shellholder design, just means that you have to remove the bolt, place a round on the bolt, insert into rifle, fire, repeat.
One upgrade is to a better muzzle brake, every Griz that I've shot with a better brake on it was a major improvement. Their standard tank brake doesn't do much in the way of reducing recoil on the rifle. You can get one of the shark brakes from Serbu Firearms, call Mark and tell him what you have and what you're looking for. You can also try Armalite, they used to sell their AR-50 brakes but you might need to have your threads on the barrel redone for it.
Other then that the Griz is a decent rifle and you'll definitely like shooting it. The next thing you'll be looking for is a place to shoot it at longer ranges. 100-300 is okay if that's what you have but it gets old quick.
For a inexpensive scope that will hold up, look at SWFA's Super Sniper scope. They run about $300 but guys have had decent luck using them. What you need is at least 3" or more of eye relief or you'll get scope eyed from the recoil. The other is a company with good customer service, that way if you have trouble with it, you know it will get taken care of.
If you have the money, buy once cry once and buy the best scope you can afford. Nightforce, US Optics, IOR, Schmidt and Bender, Leopold Mk-IV, March... It'll cost as much or more as your rifle but will last forever and if you sell the rifle and buy another .50, just transfer it over.