Well I've just had alternator problems. My bearing seized in my alternator so it needed to be reconditioned. Before it seized the light was coming on every once in a while. The local auto electrician did it for me for a very good price and replaced the bearing and the brushes.

DD is right however. Start with the easy things first. Check your fuses, Test your battery. Don't assume its the alternator. There are other elements in the charging system. No sense paying to have your alternator fixed if thats not the problem. Identify the problem first.