Leak in Heat Exchanger

I have a American Standard Gas Furnace. Model # AUX1C100A9481AB. I started receiving a pressure switch error and after doing all the basic checks I couldn't figure out what was going on so I called a professional. After 5 hours of troubleshooting, the technician was finally able to determine what the problem was. He performed the "water test" and found that water was leaking out of the secondary heat exchanger above the blower deck. The breach was causing the pressure differential to be 1.41 on a 1.4 IWC rated pressure switch which wasn't enough to "make" the switch. I have a few questions: 1) Does this make sense? The technician suggested I would need to replace both the primary and secondary heat exchanger. 2) How much should this cost? The furnace is still under parts warranty. 3) Am I better off replacing the entire furnace or replacing the heat exchanger? Thanks in advance for your help.