Keep in mind that if you mess up tempering of 'fine chocolate', you can always heat it back up and do it again.
All you are doing is trying to make one of the three types of chocolate crystals the dominant one, and form the crystal lattice.
This article chocolate alchemy describes it. In practice, having a fast digital hand thermometer is really helpful since you can actually see the changes at the critical temperatures.
As far as the Nestle stuff goes, try practicing with them as they are. I'm afraid I can't advise to throw good cocoa butter into it. You may be able to get chocolate ice cream mileage from your 8lbs. Otherwise, just go ahead temper your favourite chocolate. Worst case, a badly tempered good chocolate still tastes great.
Tempering is a process used to give solid chocolate a uniform appearance and texture, as well as to insure that those qualities are shelf-stable. Most commercially available chocolate is already tempered to some degree so that it has a pleasing appearance and texture for customers to enjoy right out of the box/bag.
Tempering is required when the final product will be made of solid chocolate or the chocolate is a component in an unadulterated state, especially in candies that will sit at room temperature. These would include molded and enrobed chocolates such as chocolate bars, bonbons, leafs, and nests.
Recipes that add chocolate to other ingredients such as dairy, flour, and sugar can be made with either tempered or untempered chocolate because the structure of the chocolate fat crystals is no longer the dominant source of structure and texture. Examples of this include cookies, brownies, ganache, ice cream, and cakes.
There is no normal application where untempered chocolate is required and tempered chocolate could not be used. The only application I have been able to think of where untempered chocolate would be desired/required is something made for the express purpose of training and/or testing chocolatiers or chocolate tasting professionals.
Best Answer
There are two issues, both of which make this a bad idea:
You temper chocolate to give it a hard, snappy texture. Adding any liquid would be counter-productive to this goal.
All normal alcohol has some percentage of water in it (as much as 60%, for example, for a typical vodka). Small quantities of water will make chocolate seize turning into a grainy, paste-like mess.
If you really want to flavor chocolate that is to be tempered, you should use a pure essential oil. These have no water, and are used in very small quantities.
Still, the better bet is to flavor the filling or other ingredients in whatever you are making.