Kevin,
I think this may be your relative: (from the IL State Archives Databases)
Pvt. Narcessus J. Young; Co G, 27th IL Inf.
Residence: Mercer Co., IL; age 21; 5'8 1/4"; brown hair, gray eyes, dark complexion; single; farmer; born Rutland Co., VT.
Joined 8-20-1861 at New Boston, IL by H.B. Southward for 3 yr. Mustered in 8-24-1861 at Camp Butler, IL. MO 9-20-1864 at Springfield, IL by Lt. Sumner.
Remarks--none.

A history of this regiment can be found at the IL Civil War Project website <http://www.rootsweb.com/~ilcivilw/> Click on the regimental number. Also, check out the scrapbook pages to see if anything is there related to the 27th IL Inf. There is also a link to various burials of IL veterans from states other than IL.

To verify that this person is the same man as your relative, you may want to locate the G.A.R. Post for the town he died in (or nearest post to that town). Dennis Northcott has recently published a book for G.A.R. Death rolls (1883-1948) for Kansas, Nebraska, and Iowa. I don't have a copy of this yet, but he may have put the Post #'s on his website, or perhaps the actual location of the original G.A.R. records for Iowa. His site is at www.ngpublications.com

Also, he probably has a government stone indicating his service. I'd try the library where he died at to see if they have cemetery listings, etc.
Hope this helps.
Ann