This is a very camera friendly event that I've shot before. One day is enough but you can get a lot of action and old time images.
Admission is $12 for adults $6 for kids, parking is $5 per car. There is a slight reduction for advance sales (see the website below). The terrain of the place is open fields with hills on both sides. Most walking is on nearly level ground. There is a food concession (not really great but adequate, personally, I'd bring my own lunch) and bathrooms are available (I don't recall any great problem with this).
The daily activity schedule is here: http://www.civilwardays.net/cwdschedule.html
The battles are lots of fun fast telephotos [masked] or[masked]) are useful for these. You also can go into the local village or encampments during the non-battle or more active periods of the day and get nice old time images and more normal lenses are useful for this. I've shot some black and white film at this too for fun as well.
Much more detail here: