In theory, everyone who works at a gun shop should know how to mount a scope. However, I have had two occasions where the guy at the store mounted the scope with the wrong rings. In general, is it better to mount the scope yourself on a bolt gun? I generally let the store do it since I figure they will have more rings available.
I worked in a Cabela's gun department part-time for a year and a half some time ago. I worked in the "Gun Library" (used guns, including high end guns because I knew enought to value them by condition given our local target market when I bought for the store) but interacted with the guys who sold new rifles and scopes and installed scopes for customers. Some of these guys even knew which end of the rifle was the dangerous end, which direction was correct for the bases, and which base and rings to use when the receiver had its mounting points on two different levels. A few knew to use a torque wrench on bases and rings and even confirmed the recommended torque settings for different type rings. One or two even knew the benefits of rear rings that allowed external windage adjustment so that you could bore sight the gun with the scope's windage at mechanical zero. I mention this because most of the the sales personnel at most gun shops are minimum-wage clerks with no gunsmithing experience whatever. Further, they are under some time pressure to get the job done and get back to flogging product. Trusting a good rifle and scope to their ministrations is likely to produce suboptimal results. When I shoot at the local public range, I see most of the shooters with new rifle/scope setups not being able to hit paper and many have scopes that come loose with recoil.
Mounting scopes is a relatively easy process, and Wheeler sells a kit that includes a DVD with instruction as well as a good torque wrench, lapping bars and spirit levels to align the scope and reticle correctly. Vortex has videos on their website to show you how and help you (I happen to use Vortex Razor Gen 1 and Gen 2 scopes with appropriate precision matched rings on my precision rifles...buy once, cry once). Bore sighting is also relatively easy, either with a laser, available for a little as $25, or a kit like the one that Bass Pro sells with rods of different caliber that attach to a sighting grid to allow bore sighting of almost any rifle you have.
In my experience, getting the bases and rings on with the right torque and the rings lapped to ensure full contact of the rings with the scope tube, getting the scope and reticle aligned correctly (easy...just use a small level on the receiver to het the rifle vertical in the gun vise and hang a string with a weight like a washer or nut on it to set up a reference to vertical to align the vertical crosshair), and getting the eye relief right to get a full picture while keeping a safe distance from the scope eyepiece are the critical steps. If you do this all correctly, bore sighting that will get you somewhere on paper at 25-50 yards is also easy. After that, sighting in becomes very easy.
Net, net...DIY will get the best results if you have a gun vise (I use a Tipton's), the correct tools (I like Wheeler's) and the appropriate rings for your scope (Vortex has customer service e-mail that recommends the best rings for your scope, rifle and application. I have also contacted Leupold customer service for recommendations when I mounted their scopes on my hunting rifles...I have typically used the STD rings and bases to take advantage of their external windage adjustment on my hunting rifles). Manufacturers want to help you so you'll be happy with and use and recommend their product.
Good luck and good shooting.
