A few AJAX/jQuery additions to an existing script

I have an existing script that I have already had made for me. I need a few small additions to the script. I need to Submit a form (1 text field) through Ajax, Generate a 4 digit pin number, check it against a database to make sure it doesn't exist and then return the 4 digit pin number all without the page refreshing. I need a php function to generate the same pin number from a URL [login to view URL] If the account= contains a number then it generate the 4 digit pin, if not then we will wait for the user to input the account number on the form and hit generate pin. Lastly, I need a function that runs each time the script does. It checks the database and if the last pin was entered 2 hours or longer ago it needs to delete it from the table. Same functionality as a cron job but runs only when the script is launched. I know this changed will take less than 1 hour so don't give me un-realistic prices. I need this done within the next day.