Require PHP User interface (which we can easily do ourselves). However, we want the option for users to add credit to their account (eg: $1USD = 250,000 points). Users can then navigate the site and purchase upgrades (with their points) and we need their user account to reflect the credit balance increase/decrease as well as a confirmation in their profile that they have purchased that product (visually able to see a graphic or something along those lines). So in effect, the credits spent will need to upgrade other areas of their profile but also reflect the change in a running balance next to their username etc.
If you require more detail, please let me know, but this is a rather simple job - it's just I cannot find resources anywhere to help.