If the rifle has already been drilled and tapped, there's no reason to have it done by a gunsmith. Do it yourself. Find a good, solid base, get some good rings, a lapping bar and compound and learn how to do it yourself. It ain't brain surgery. If you're worried about in-line bore-to-scope, you can do as Hoghunting recommends, and buy Burris Signature Zee rings with the polymer inserts. They'll give you plenty of slack for adjustment.
If you're comfortable with the idea that the holes are truly plumb and in line with the bore, you can even step up to the BIG names and go Badger et. al. for your rings--though there's very little forgiveness in those rings. Your base might need an incline if you intend long-range shooting; 20 degrees is pretty standard for an inclined base.
Be sure to zero your scope's reticles first before you adjust it in the rings and tighten the screws on your installation to hit paper. You want as much adjustment as allowable for the W and E knobs, and if the scope starts out zeroed, you'll have the best chances to preserve the maximum adjustment possible.
With no previous gunsmithing experience, I did my first scope install successfully and have done 4 more since then for the price of a lapping tool and compound (about $17). If you go the Burris Signature Zee route, you won't need to lap the rings. My first scope was also a Leupold Vari-X III; the next four were Nightforces. Good practices won't jeopardize your scope.
Here's a coupla articles, and I'm sure you can find a Q&A here on this forum with a search.
http://findarticles.com/p/articles/mi_m0BQY/is_9_49/ai_105642911
http://www.pyramydair.com/site/articles/scopes-part2/
with an expensive
quality set of rings and comparable mount (i. e., Badger, Nightforce, USO), most folks don't even lap:
http://www.snipershide.com/modules.php?name=Content&pa=showpage&pid=25
If you wanna get fancy, there are scope leveling tools and boresighters that you can use to help, but they are mainly "convenience" tools. With either ingenuity or patience you can substitute brains or sweat for them.