Sorry for your situation, but it is not the dealer's job to tell you about the car's potential problems. You should have had a mechanic examine the car before buying it. This vintage is listed as 'much worse than average' for 'transmission minor' and 'drive system' in Consumer Reports.
Unless you have something else in writing, the dealer's not obligated to give you your money back. You may need to talk over your options with a lawyer if you don't want to accept the car once they fix it.