My 07 Murano is due soon for the 22.5k mile service and I'm going to bring it to the stealership since it's still under warranty and I want to do this official for this reason. About how much is this going to cost?
There IS no 22.5K service required on Muranos by Nissan. Your dealer might offer one so they can make $$ off unsuspecting customers, however.
Of course, 22.5K would coincide exactly with the 3rd, 7.5K interval oil change, and may also be the right time for air and in-cabin filters. The first 5 oil changes came with my Mo, so I took mine in at 22.5K to get the 3rd one done. Nothing else was touched nor recommended at that time (nor at the next 2 oil changes, the last 2 done by my dealer). Filters are so cheap and easy to do, there would be no reason at all to go to a dealer for those.
Personally, I'd NEVER go to a dealer for an oil change either if I had to pay them for it. First, it takes less time and inconvenience to do it myself (my dealer is about 10 minutes away from me), second (more importantly) my local dealer doesn't use full synthetic, and finally, I use oil changes as a convenient interval to rotate my tires and inspect underneath my car.
So, to answer your original question, other than an oil change and maybe those 2 filters, your 22.5K service will cost $0.