Is there a good video that describes how destination points works? For example, how long after I change my property to destination points do I have to use them? Can I change them to Marriott reward points once I change them to Destination Points?
No videos that I am aware of. I would suggest that you contact the sales person that sold you your MVCI property. If for some reason that person is not available, speak to any sales person. Or, if you happen to be near a Marriott property that has a time share sales office, just walk in and ask to speak to somebody. As an existing owner, they should be more than happy to talk with you and answer your questions.
I suggest you check the MVCI website "How to get the most of your time share" and attend one of their webinars focused on the points system. I have attended a couple of them and have found them informative and the Q&A session helpful to answer specific questions.