I agree with Trip about asking John Heald. I think in the past he has forwarded the person that is asking contact info. Then is up to the crew member to reply or not. I find the crew that I have sailed with several times enjoy staying in contact. Have never tracked one down though.
Another option may be to ask on Facebook. There is an open group called Carnival Cruise Lines Crew. Just search for it. Someone may know them as the crew often change ships and know crew on other ships.