They seem to have a really good course. I talked to another INGOer who went there, and he said he loved it and was really happy with the program.
ETA- link doesnt take you right to the page, but if you click on technical certificates, then scroll down to gunsmithing, you can read a brief description on the course.
And I recommend against doing gunsmithing online. I think its more of a hands-on thing, and not something you can perfect by reading online.