in terms of difficulty.... 1.5 (on a scale of 10)
in terms of stuff needs to be removed to get to the belt...3 (none hard just a couple # of things before you can get there - rear storage shelf, carpet on engine cover, firewall carpet and metal shield).
Here's a recent thread w/ more info. If you have the Bentley manual, it'll tells you how to route the belt. If not, there's definitely info here just do a search for it.
Recent Thread on Poly-rib/Serp Belt Replacement