Script Modifications - PHP/MySQL Expert

I need some modifications made to an existing script that is already installed and running. The job requires PHP/MySQL/Javascript and Smarty Template Engine experience. In the attached spec sheet I've detailed 3 modifications in addition to a 4th optional modification. Please state if your bid includes the 4th modification. The script is well documented and logically the modification are pretty straight forward but I'm not sure how long to expect the work to take which is why I used a custom budget. I will make my award based on experience level, feedback, delivery time and price. I have further modifications planned and would prefer to use the same developer for this work as well. Please see attached Spec Sheet and dbase schema for full details.