As of right now, your choice is to collect the 120 ECE credits over 3 years. Re-passing the examination will not give you the needed credits for recertification (it only gives you 40; I have no idea why). So no, you do not necessarily have to pay to take the exam again.
When did you earn your certification? If it was prior to Jan. 1, 2008 then you need the 120 by Dec. 31, 2010. If you earned your certification sometime this year then you have 3 years from that date.
There are a large variety of ways to earn your points... attending conferences, taking classes, participating in webinars, listening to podcats, reading books, writing articles, etc. As you can see in the Delta portal, they all have their own value in points.
Hope that gives you the information you were looking for. If you need anything further or more clarification, feel free to ask.