I have a 2011 Mercury Milan Premier with a dead passenger side brake light. I am trying to figure out exactly what I need. On ebay and at a junk yard the prices are quite high. I guess that is because it is an LED light. I noticed on ebay (and I think the junkyard) they are selling the complete light unit. But, do I need the whole unit, or do I just need the LED. What do I really need to buy?