It's a different kit for the 2.5 versus the 3.5
http://eibach.com/cgi-bin/html...09102
You can see that the part numbers are different, even though the drop amount is the same. This is most likely due to the fact that the two models have a different weight especially on the front, thus needing a different stiffness.
On the price of install... try finding a friend or even friend of a friend who's got some decent experience and offer them beer / dinner have them help you install it! That'll definitely be the cheapest way to go... or if the dollar is a big concern, you could always try the DIY guide from here and I'm sure the guys around here will help you if you run into troubles!