Tough situation. The exact reason why I stopped using Raid 0. I think Raid 0 does give some nice benefits, but my data is too important.
AFAIK, all your data is currently in tact. However I'm not sure what 'initialization' will include. If it just creates the RAID structure, you should be ok. (The current sturcture will simply be overwritten by the new one, leaving data in place) But 'initialization' could involve more than that which will put your data in jeopardy. But you prolly knew everything I just said.
I do have to ask, why did you pick the JMicron controller over the ICH10R?