There is no car-rental right in Sturbridge. The closest pickup point is Worcester, MA.
Most of the name brands are available there (Hertz, Avis Budget, et.al.) and you can find info about them on their sponsored web sites. (for example at: www.budget.com).
There are local, private transportation services (King Courier, Ruben Transportation) and a quick Google search will get you to those websites for fees.
There are no public transportation services in Sturbridge.
The easiest way to get around Sturbridge is by your own car. The roads are not difficult to find with a local map. The traffic is not difficult to manage even in the height of tourist season.
The closest air service to Sturbridge is in Worcester,MA.
You can take PeterPan Bus Lines to and from the airport and Worcester (schedule is limited but price is right) or you can use one of the taxi services (see "transport options" in website below) which will be fairly expensive or you can use some of the private transportation (Ferris Transport, Ruben's Transportation, King Courier) which are readily available but will cost. You can also rent-a-car at the Worcester terminal (Hetrz, Budget, et.al.).
Once you are in Sturbridge, there is no local public transportation.
Peter Pan has two drop off points in Sturbridge- one at the bus stop by the information centre which is a quick walk to Sturbridge Host Hotel. The other is right outside Old Sturbridge Village. These stops are good if you're coming to Sturbridge from the outside and want to be dropped off at the hotel where you can walk around the area for a night or two, go to the village for the day, and getting back on the bus to where you came from. Or meeting people with a car. But if you are staying near the first stop off point and want a ride to the village, you could take the bus between at least these two points.
You do need some sort of transportation but you can get a small chunk in through just the bus. Get times at the stops or online.