Our group came into the visitors center from the parking lot, and we asked about the tours. First, we watched the 17 min movie in the theater, then went outside to walk in and through the different buildings. They had actors dressed up that you could ask questions to about Abe Lincolns stay there. After that, we took a stroll back inside the visitors center to walk through the museum of Abe Lincolns time spent in New Salem.
You can do all of the activities for free. However, there is a suggested $4/ person donation. The parking is free. There is room for RV's to park in the parking lot. This self guided tour takes about 2-4 hours depending on how much you want to soak in.
Make sure to dress appropriately for the weather as you are walking outdoors mostly. I did see people with dogs and strollers. There is an air-conditioned visitors center with a small museum inside. They have bathrooms in the visitors center and about halfway through the cabins.
I would suggest bringing your own water and snacks.. Although there is a water fountain in the visitors center. They do have picnic tables and pavilions to eat at outdoors.