Element, wind melds worth it to reach minimum han requirement?
Your understanding is correct.


  Yakuhai (役牌), also known as Fanpai (飜牌), is a 1-han yaku consisting of a pon/kan of any of the following:
  
  
  Dragons (elements)
  Your current seat wind
  The current round wind (typically east or south)
  


As it is a yaku, it will net you the 1-yaku minimum required to complete your hand.  It doesn't matter if the hand remains open or closed, so calling a discarded tile to complete the set is perfectly legal.

Whether it is the best choice in any circumstance is highly dependent on the rest of your hand; the point value of an open set is only half that of a closed set, and there are many other potential yaku which are unavailable when a hand is opened.  In particular, you lose out on the ability to call riichi, which would also provide the 1-yaku minimum and give you a chance for ura-dora as well.