The extended crew cab is the mega cab I think. 2006 was the 1st year they had that. From the little picture I would say it is a crew cab not a mega one (extended crew cab). Here is the mega cab
And here is the crew cab
Also when I replaced my ball joints a couple months ago, I only did lowers because of lack of funds. But doing all 4 if you can afford it definatly won't hurt anything except your pocket. I would also make sure you get a good quality ball joint like moog that is grease-able. If you need help I wrote a step by step process (kinda) of how to do them.