Wandering is usually due to component failure, but can be due to improper alignment. If you have manual steering, the first thing to check is the steering gear. Can't recall the specs, but the shop manual tells how to adjust it. If you have a lot of play in the steering wheel, have someone turn the wheel and watch to see if the pitman arm (on the bottom of the box) moves immediately. If not, the box needs adjusted. Also check ball joints, tie rod ends and wheel bearings. Are your tires properly inflated?
If you're not sure, go back to the shop, tell them you had the truck aligned there, and that you are having problems. It should only take them a few minutes to check. I don't recommend going in with an attitude. This is one time where playing stupid can help.
