I menioned to my business partner that I wanted out of the partnership. She locked me out the next day and changed alarm codes. Do I need an attorney?

Possibly. It depends on the terms of your arrangement. If you were true "partners" (in the sense of having entered into a legal partnership), you should not be excluded from the business. If you have some other arrangement, such as being shareholders of a corporation or in a joint venture, that answer might be different. Accordingly, a consultation with an attorney would be appropriate.