Atilla mentioned to "be cautious" before agreeing to a transmission flush. To elaborate, there have been several posts here where people suspect that a flush may have lead to failure of their transmissions. Some advice says to avoid it unless you know it's been done on a regular basis.

You may have already read this, but just in case others read this thread in the future, I thought it was worth mentioning. Search for "transmission flush" for more details.