When I first visited the site roughly 16 years ago this is all I remember being there in the way of signage, though there probably was a general NPS info sign as well.
Since then this really nice monument to the 9th Connecticut has been placed. It has really nice depictions of digging the canal on each side as well as pictures of officers. It is still so shiny that the pictures of the officers didn't come out very good. Probably had a lot to do with the lighting so I'm sure better photos could be achieved on a different day, or even time of day.
All in all there is now quite a bit to see at Grant's canal.