Alter osCommerce Affiliate Utility

We currently use an Affiliate utility that a previous programmer installed on our osCommerce shopping cart ([login to view URL]). We need it to be altered so that instead of calculating commission by percentage of the referred orders' totals, it calculates based on the number of orders the affiliate refers per month (that is, in MySQL terms, the quantity of affiliate_orders_id created in association with their affiliate_id). To make things more complicated ;) -- we have three classes of affiliate membership, each with different pay scales ([login to view URL]). The classes are based on the average order total at the end of the month. SuperAffiliates' average order total is $250-$324; UltraAffiliates' average order total is $325+. It'd be great if the affiliates were automatically classified at the end of each month, so we know how much to pay them... Incidentally, we'd like a script written so that our Accounting department is notified by email whenever the amount earned by an affiliate reaches $50, so they can send them a check. The current utility has an invoicing area, but it's still on the percentage commission system, so it's pretty much useless. We also need a separate thing written so that the affiliates can refer customers to our "Free Downloads" page ([login to view URL]), and we'll pay the referrer per unique email address captured (currently, customers are suggested, but not required, to enter their name and email address before downloading). We'd like to be able to assign different payout rates for different downloadable files...