Big question would be, what is your budget? You could spend a lot of money getting that file to a level where is could consistently shoot 800 yards. At a minimum it might require a new stock with bedding and a new trigger. Then a good scope. After all of that you may discover you need a better barrel. If the barrel is needed, the rifle might not be ready for this seasons hunt.
Also, do you hand load your ammo now for the rifle or does it shoot factory ammo? How well does it shoot now?
Might be better to purchase a new rifle that is setup for long range. Savage has a good rifle called Long Range Hunter. Ruger has a new rifle out named Ruger Precision Rifle. The Ruger in 6.5 Creedmoor would probably get you to 600 yards with Hornady factory ammo chambered for 6.5 Creedmoor with the 140 gr. A-Max bullet.
Check these two rifles out.
Ruger Precision Rifle™
Savage Arms