Just finished my installation this weekend. It took me more than a couple of hours from start to finish including several breaks and listening to my neighbor's "vacation" plan 
Kudos to Ryan for making an "easy to follow" installation guide for people (like me) who is not mechanically inclined. 
For those of you who want to do this your self:
1. If the Z is your only car, make sure you have all required tools (listed on Ryan's guide) before starting the project.
2. Take a few minutes break every time you are stuck or frustrated on something. Get up, take a fresh air, get a beer or something, then start again.
3. Wear a thin rubber glove on your right hand since you will be working in a thight space with metals and wires.
4. Putting two milk crates next to the side skirt covered by blankets (to protect the side skirts from getting scratched) would allow you to lay on your back while working under the dash board without removing the seat. Thanks Stino! 
5. E-brake should be engaged at all times. I put mine on 1st gear & e-brake just in case. 
6. My back was sore the next couple of days so do it on Saturday instead of Sunday.
Edit:
Just took a test drive with RJM pedal installed, Wow! Couldn't believe it's the same car! Shifting gears feels soooo smooth.... Stop and go is no longer an issue. I've been driving the Z for 2 years for about 20,000 miles and never thought the stock clutch was that bad!
I highly recommend this pedal to ALL MT owners!