Go figure. I just did that on the 325 three weeks ago. It is not a terrible job but VERY time consuming, I think I did it in about 6 hours, taking a lot of breaks and taking it slow since it was my first time, and gets kinda frustraiting at times because of the tight space and all the parts you have to remove to get to that valve that as I say is in the deeps of the sea! You don't have to take the intake mani to do it.
Let me tell you, $480.00 with parts and labor is a REALLY good price, taking in account that the CVV kit (with all hoses) is about $200.00. The funny part is that it didn't solve my problem, wich was a whistleing noise, that NOW I discovered is the alternator pulley (after I got an stethoscope...). I considered that job as a part of my DIY training! lol. On the positive side, I found a CVV kit for sale on the classifields on bimmerforums, and the guy sold it to me for $60.00 shipped, so that was basically my cost.
But if you ask me, I would still do it my self to save 300 bucks. Here's the instructions I followed, they are for a 2.5 but all M54 motors are the same, the only difference I can think of is that you need to remove the strut bar on the X3, whick is held by 4 bolts IIRC.
http://www.bimmerfest.com/forums/showthread.php?t=323335