Rebecca,
Brigadier General Turner Ashby died 6 June 1862 near Harrisonburg. Joining the 7th Virginia Cavalry was seen by young men in the Valley as a sort of romantic adventure, and many joined up just to serve under Ashby. The 7th Virginia had grown to 29 companies, which was too large to be commanded effectively. A good career professional officer would have had difficulty commanding so many men, and Ashby, while charismatic, was not a professional army officer. His unit, while showing moments of brilliance and extreme courage, suffered from drunkenness, security lapses, and lack of discipline.
As for your GGGG grandfather, look him up at the Civil War Soldier's and Sailor's Database maintained by the National Park Service.
http://www.itd.nps.gov/cwss/soldiers.cfm
The system lists John H. Boone as serving in the 7th Virginia Cavalry.
You can look into his service record at the Library of Virginia in Richmond, in the microfilm room.
Also, you can read about the exploits of the 7th Virginia Cavalry in the book by that name (by R. L. Armstrong), which is part of the Virginia Regimental History series. They are very well-written, and cost about $25, although your local library may have a copy or can get one through interlibrary loan. These books contain a list of all the soldiers that served in the unit, along with information of that soldier's service.
I hope this helps.
Jonathan White