Civil War Battle Map of GETTYSBURG

I have no clue how to get started, but I think a Battle Map of GETTYSBURG would be really cool and other Civil War battles as well.
Its could be built along the lines of the WATERLOO map. Just over lay the Gettysburg map but the tactics, objectives, all the same or similar to fit with the actual battle
Generals Lee and Meade HQ's.
Various artillery positions for bombardments.
Terrain areas such as Missionary Ridge, Cemetery Ridge, Little Round Top, Big Round Top. Culps Hill, Wheat Field, Devils Den, Town of Gettysburg, Peach Orchard, etc etc.
Battle Commanders: Pickett, Chamberlain, Longstreet, Buford, Jeb Stuart, Hancock, Ewell, Hood, etc etc.
Since it was a 3 day battle and units changed positions, then not sure how to set up the units, but Waterloos was not a single day battle either.
here is a sample map I found on the internet.
http://www.loc.gov/shop/images/catalog/items/enlarge/enlarge_mapofbaofge1.jpg
What do I do next??????
Its could be built along the lines of the WATERLOO map. Just over lay the Gettysburg map but the tactics, objectives, all the same or similar to fit with the actual battle
Generals Lee and Meade HQ's.
Various artillery positions for bombardments.
Terrain areas such as Missionary Ridge, Cemetery Ridge, Little Round Top, Big Round Top. Culps Hill, Wheat Field, Devils Den, Town of Gettysburg, Peach Orchard, etc etc.
Battle Commanders: Pickett, Chamberlain, Longstreet, Buford, Jeb Stuart, Hancock, Ewell, Hood, etc etc.
Since it was a 3 day battle and units changed positions, then not sure how to set up the units, but Waterloos was not a single day battle either.
here is a sample map I found on the internet.
http://www.loc.gov/shop/images/catalog/items/enlarge/enlarge_mapofbaofge1.jpg
What do I do next??????