Thanks to everyone for more suggestions! I have requested brochures from all of the companies that you have recommended. It seems that several of the tours for 2009 aren't posted until Sep or Oct. I am going to keep researching until then. I'm sure I will have more questions when that time arrives. Thanks again!

Haven't read other posters' replies so sorry if this is duplicate. Check with your alma mater, or your local university or community college-they often have guided tours.
Good luck!