Unless you have indications in the handling that the caster is off, then it's not worth paying an alignment shop. Caster is only adjusted by stuffing tapered shims between the axle and the springs, and camber can't be adjusted. The only other adjustment, and what a shop will charge you $50 to adjust is something you can do in an hour or so in your driveway. Here's how: Toe in is very important, but easy to set. Measure up from the ground to the middle of the hub, then put a strip of masking tape across the front tires at the same height, front and rear. Then find the middle of the tread, you end up with a big + on the tires. Then just measure the distance between the + signs on the front and rear of the tire, adjust till the front is about 1/8" less than the rear. It really helps to have a second person to hold the other end of the tape steady on the other side of the truck.