Definitely talk to people who have done it before! It'll make things a a lot easier and save you the grief of having to rebuild if it doesn't work first time out.
Our club is in the process of building a new astroturf track and up to now it has taken 2 months of hard work on weekends and it still isn't finished completely!
Here is the thread where I have been posting pics of our progress -->
http://www.oople.com/forums/showthread.php?t=43151