osCommerce PHP Script Modification

We currently have a 2003 version of osCommerce which requires a minor modification. At the moment, if members forget their password, they have the option of requesting a temporary password when resetting their password. The script will email them a temporary password, however, there isn't the option of later changing this password. We do however posses a script designed for the affiliate section of osCommerce which allows for affiliates to change their password. We are wondering if it would be possible to modify this script to allow for members to change their passwords in the same way (we've attached a copy of this file). As we're working on a micro budget, please take this into consideration when bidding. As we'll be changing the platform shortly, if it's too much we won't be able to award this project.