What is the fork from originally, and what spec headset did it have originally? as if you can ID them, and compare to the bearing that the Orbit has, you may be able to just use the original fitted (on the basis that you haven't wrecked it by trying to install over the top.

Got to look at this and think that your way out your depth here, either a case of asking/researching before you cause expensive damage, Park tools site as mentioned, or Youtube for how to videos