FYI, the New York Times on Oct. 18, 1915, had an obituary:
"James Gillen, one of the crew of the Confederate Ironclad Merrimac when she was defeated by the monitor, and for many years in the towing business at Greenpoint, L. I., died on Saturday at his home, 171 India Street, Brooklyn, in his seventy-fifth year."
Sharon, there is also a bit more in Quarstein's book on the Virginia. He notes spellings as "Gillan", "Gilliam", "Gillen" and "Gilland".
There's also a genealogy query on him from 2002 that I can point you to.
Please contact me through my site http://CSSVirginia.org as I'd like to add some of his biographical info to my listing for him.