This might seem surprising, but the IRS is a great resource for help with their forms. You can access forms and instructions online at irs.gov and talk to a real human at 1-800-829-8815.

I am not familiar with a "group exception number". But if you mean a tax identification number (also called an employer ID number, EIN, or tax exempt number), your organization needs to file out a Form SS-4.

Where can a PTO go for help on a 990? They have never had to file and now are looking for help. They need to know how to get a group exception number. Any help would be appreciated.