The Legacy has been through 5 generations. For most generations, all available engines were 4 cylinder Subaru boxer engines. More recent models have 6 cylinder options, including a 6 cylinder boxer engine on the 4th generation models.
The first generation was sold in the United States from 1990 until 1994. The second was sold from 1995 through 1999. The third generation was sold from 2000 to 2004. The fourth generation from 2005 to 2009, and the fifth generation from 2010 onward.
Trim levels started out as standard, L, and LS. The LS was changed to the LSi and the standard option was dropped in 1991. The Sport Sedan and Touring Wagon were introduced in 1991 and 1992. In the second generation, the GT and Limited models were introduced. The rarer third generation trims include GT-B, Revision D, Blitzen and Avignon.
The Legacy has been sold as a sedan and wagon. To find one used, just go to any used car lot. These things are everywhere. You can find some good deals by shopping on eBay for your next used car.