Register our business in Illinois

Hi, We have recently received an office address in Chicago in order to expand our business into the US. We now wish to register our business with the State of Illinois. If you are a registered accountant with an FEIN, we are looking to have you complete all the required paperwork to register the business. The address is for now a virtual address that we recieved through Regus. Regus would also like us to fill out some paperwork and get it notarized: USPS 1583 form. Please reply with your experience and how long this will take. We would like to finish this ASAP. Thanks and Regards, Yan