The critical mods would be: an new barrel and trigger assembly. If you don't want to spend alot of $$$ on a trigger assembly, a Volquartsen Target Hammer would immediately drop you stock trigger pull down to 2.75-2.5 LBS. This would increase accuracy.
The next thing is get a new barrel. Budget barrel - Butler Creek (Stay away from their carbon fiber barrels, their other barrels are good though) or Green Mountain.
High end barrels for ultimate accuracy - Volquartsen or Lilja.
Need help with any of these give me a haller. I have a few bits that can help and I can give you the names of places where you can get barrels, stocks..etc.