Hi Lowanne,
When I got a second opinion, I asked and did research about which institutions nearby had a comprehensive cancer center. Most of this I did on the web. The links that Danny is referring to are:
The National Cancer Institute Cancer Center Programs
url: http://cis.nci.nih.gov/fact/1_2.htm
and
The National Comprehensive Cancer Network
url: http://www.nccn.org/members/network.asp
You might want to investigate institutions relatively nearby such as the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.

Most of these centers have web sites with contact information. Some specify who to contact for second opinions. Once you've decided on where you'd like to get your second opinion (and perhaps members of the forum who are geographically near to you can make some suggestions), you should then inform your current doctor(s) that you are getting a second opinion and provide them with information on where to send all of the information that is required.

In my case, this included slides from the margin, pre-surgery ct scan, plus surgeon's report. My doctor encouraged me to get a second opinon and shipped the necessary stuff in less than a week. Hope this helps. Best of luck, Sheldon