I did mine on my 3.0 and if the 3.4 is at all similar I would suggest saving yourself the money and doing it yourself, the hardest part for me was breaking the crankshaft bolt, which for me on the 3.0 required me making my own tool out of a small piece of angle iron. I suggest purchasing a FSM (factory service manual) and taking it on yourself, I did it that way before I was a member of this forum with only my FSM, I do realize that these are two different engines but assuming that the process is similar, if I did it you will be just fine. Also if the water pump is tucked down there like it is on the 3.0 I would suggest replacing that as well depending on your milage. I am guessing that if you take it to the stealer you will be out something like 3-400$ maybe more? Good luck with whatever you do.
-rbrach