Completion of web-purchasing (PayPal) and product activation

We are preparing to launch a software product called Smartline Project. Please have a look at www.smartlineproject.com. The web-designer who built it is unfortunately busy and will not be able to complete the website any time soon, hence this post. 99% of the content is up, and I can upload the remaining items: demo version file, user manual, etc, when they are ready. What I need is to get the Product Purchase and Product Activation components completed. The way it is designed to work is that all the possible purchase options will be on the Purchase page, and each option has its own PayPal Buy Now button. So each button needs its own code, must fire off the PayPal process and then arrive at a unique page when the payment is processed where the user can download the relevant product they have purchased. The database has been built to cater for this process. See attached Database Map which shows roughly how it is set up. My web designer put together the attached Task List document which outlines the outstanding tasks. Any suggestions to improve the purchasing process will be considered, but only if it doesn't require a whole lot of additional work or a complete redesign! Time is of essence with a planned launch date for end of January 2010. Thank you in advance for your interest.