The credit bureau usually has 30 days after receiving your dispute to investigate and verify information. Typically, the credit bureau will reach out to the company that provided the information and ask them to investigate. The credit bureau is required to send you the results of the investigation within five business days of the completion of the investigation.
Checking your own credit score will not impact it in anyway positively or negatively. There is a difference between doing a soft credit check, which is what utility companies, landlords, or cell phone companies may do to see if you qualify for perks such as not having to pay a downpayment, and other types of credit checks that lenders usually do, which are called hard credit inquiries. Hard credit inquiries will typically reduce your score by a slight amount, but only temporarily until you start paying your loan.