Okay I assume that you are talking about the passenger side vent... here is what you need to do....
Take a flathead screwdriver and look at your vent as if it is a clock.. take the screwdriver and insert it at the 5'o clock and 7' o clock positions... there are 2 tabs there that you will need to depress, once that is done the vent will pop right out. once you paint it just simply push it back in, do not worry about hurting the dash when you are prying the vinyl will just snap back into place later.. Also, use the largest flathead you own, the fatter the head the easier it is to depress the tabs.
This post will be added to the FAQ section too seeing that either myself or Carckck has helped millions of times on this question.
BTW- Carchk is the dash master.. she was the one who answered all my questions prior to taking my own dash apart 6 times now... hehe THANKS SENSI HEATHER!