Go to http://accounts.google.com/signin/usernamerecovery and enter any email accounts or phone numbers that you've had for a while and which may have been used as recovery info. The “find your email” page can help you locate any forgotten Google accounts. On the next page, you'll be asked for your name.

Yes, your Google password is the same as your Gmail password. When you first create a Google account, it includes access to various Google services, including Gmail (as well as Google Drive, Google Photos, and more). All of these services use the same account credentials as your Google account.