The Baldwin Home Museum is a nicely preserved missionary house from the mid-1800's. What you'll find here is a house still setup with the same furniture and such as it would've been when the Baldwin family originally lived here. The home has been passed down to the preservation society so that this bit of history can be forever preserved.
You'll find maybe a half dozen rooms all still furnished. You can wonder around as much as you like, no guided tours here nor are the needed. Spend as much or as little time as you like.
Doesn't sound like your cup of tea? Then skip it, this isn't a must see. But if you have some time to kill, this is an easy stop while you're wandering around Lahaina. The price of admission is cheap and covers both this house and the Wo Hing Museum down the street.