I messaged someone who lives in Plymouth, Massachusetts concerning the trip I'd like to take. Here is his response:
The amount of time you'd want to spend here is dependent on how fascinated you are by history and such. There is only one real museum, in the proper sense of the term, and I've never visited it, so I can't give you particular details. Most points of interest are all in the same general vicinity -- the waterfront & downtown (where the museum is) -- and could be covered, though not in incredible depth, in a half day. Most tourists like to stop at Plimoth Plantation, the replica of the Mayflower, and, of course, the notorious (and anticlimactic, frankly) Plymouth Rock. There are a lot of a interesting and historic houses dotted around the downtown area, as well as a gorgeous old stone Unitarian church (where I got married, incidentally), which is next to the Pilgrims' Burial Hill. There are walking tours, though I think that they don't start until later in the season.
Hope that helps you some. And I hope that you enjoy your trip.