There were only two generations of the Silhouette. They lasted from 1990 to 1996 and from 1997 to 2004.
The first generation Silhouette was a 3-door with a V6 engine. The model was built off the GM U platform. Some features that were added through the years included the remote controlled sliding side door introduced in 1994 and the traction control added for 1994 and 1995. It was only available on the top model with the 3800 engine.
For the second generation, some new features were added. A sliding door on both sides was added as an option, and that feature became popular with large families that didn't enjoy climbing over one another just to get seated. These second generation models were sold in either short or long wheelbase form.
These cars never sold as well as Oldsmobile hoped, and usually not as well as the other U platform minivans. The Silhouette was features in the movie Get Shorty, where it was called the Cadillac of minivans in jest.
These minivans are still sold in abundance on the used minivan market. You can find some amazing prices if you check out the listings on eBay. You should also buy parts there before you buy them from your GM dealer, as they tend to sell for far less online, especially on eBay.