Hi
From memory you have what was called a Mindset.
The races (top and bottom) knock out and you either need
a) a new Mindset for the ID of the headtube (should be 41mm exactly).
or
b) check what is inside the headtube (there may be an angled ledge) and see if will accept an integrated headset with sealed angular bearings.
You then need to make sure that the depth of the angular bearing is ok (too thick and the bearing sticks out of the headtube and too thin the forks grate on the headtube.
Also you will need to prise the old crown race off and install another (either with a concave race for ball bearings or angular for sealed bearings - this should come with the headset.
Personally I'd take it to the LBS and save a lot of palaver.
ps google Mindset replacement like this
http://www.bikeradar.com/forums/viewtopic.php?f=40004&t=12931817
and from there a really useful info
http://service.specialized.com/coll...df/Frame---Road-Frame-Compatibility-Guide.pdf