Alignments should cover everything... camber, caster, and toe-in. It may cost a bit in parts to do your car, but if it hasn't been severely wrecked, it is possible to get everything re-aligned. Tires that wear only on the inside get hotter and are more prone to blowouts.
Also there is nothing wrong with a second opinion on your car. If you feel the mechanic gave you a bad diagnosis, take it somewhere else and see what they say. There is no harm in making absolutely sure you fix the problem the first time.
