Hello Jerry, Here is a good place to start:
http://www.couchgenweb.com/civilwar/nwcoicav.htm
and, in the same vicinity:
http://www.couchgenweb.com/civilwar/2ArCavhs.html
Also, you can pay a small fee to get a service record for your GGrandfather.
Just click on the red box at the top of this page.
Happy hunting!