im2-
You should be able to simply press the crystal out with your thumbs. If you are unable to, perhaps you might consider employing the assistance of a crystal press. MIght make things easier.
When putting everything back together- Start with the crystal and gasket and simply press onto the rehaut lip. Once the crystal is aligned with the cyclops at 3:00 and etch at 6:00, you can press the retaining ring on over the crystal and gasket. This may be somewhat difficult to achieve without a press, so again, if you have one this would come in handy here.
Hope this helps...
R