title: How to trigger an event on payment received in magento?
body: <p>Greetings, in Magento I want to trigger an event, once an order has been set to processing (by gateway confirmation or manually) that, example: If a general customer (id 1) spends over 100$ and the payment has been confirmed, set his group id to 4 (silver VIP, which by promotion rule gets 2% discount globally)
  I would give a bounty to this, but I'd like the answer before 2 days  O_o</p>
  
  <p><strong>EDIT</strong>: the answer I received so far is only a partial answer, also I find the links very confusing, I'm not clear on what is the minimal setup, what do i have to configure create etc... Also I'm trying to find out how to  get the paying customers id/model.</p>