Matt,
Truing (aka blue printing or squaring) simply put is squareing the boltface and the end of the action to the barrel. Usually the lugs get lapped at this point as well.
Having your action blueprinted doesnt always equate to a huge improvement in accuracy, but ive never heard an instance of it hurting it. When your building a custom rifle, it elimanates yet another variable.
Im not sure what your local smith charges, but I am having a short action blueprinted, and shilen barrel cut, crowned and chambered for 280 here in TX.
Hope this helped.