http://www.canecreek.com/tech-headsets
– you might find it there.
Without knowing exactly which headset it is, that gold ring either came off the top end – and helps to centralise the upper bearing race on the steerer when everything is snugged up- or it sits directly against the forks and the bottom bearing race sits against it, and I'd expect you to have somthing similar for the top end.
I suspect that if it came off the bottom end, you've remember taking it off the forks.
Did you, by any chance, leave a ring-like thing sitting at the fork end of the steerer tube when you sold 'em ? Cos you need that for the new forks – it's (effectively) the crown race.
Re steerer, yup, cut to length, exact length will depend on headset (they vary), number of spacers between stem and headset, length of headtube.
The part left inside the steerer is the SFN (Star Fangled Nut) – you can't easily get 'em out anyway. You can buy a new one (a little fiddly to fit straight without the right tool or some tubing) or plug-type placement (eg Hope Hed Doctor – and if you get one, read the instructions carefully…).
Don't forget the upper can only *preloads* the bearing stack with the stem bolts loosened to removed bearing play, it's doing up the stem clamp bolts that holds it together – it's not unheard of for people to get that wrong 'cos they haven't thought about it.
'Course, taking a piccie or sketching it out first might have saved you some trouble 😉