Converting a GoPro HD2 is a lens swap. I believe the IR blocking filter unscrews from the back of the original GoPro - but it isn't the case with the GoPro 2 as the filter is coated on the back of a convex-Plano element.
We tried to order a GoPro 1 lens from ragecam in the states, but it got stuck in customs for so long I had to find an alternative. It was stuck primarily because nobody told us it was there.
Anyway, in the meantime I found a cheaper solution;
Field of view is smaller, so we might swap it out for the ragecam lens at some point...
If you are thinking of changing a gopro lens there are lots of videos to give you an idea of what's in there on you tube - but I found taking the camera apart was quite straightforward. Most of the instructions I've seen use a heat gun to free the lens. If, like me, you bought the cheaper heat gun you could fin in cpc/poundland then you could try a dab of pure acetone on the lens thread.