The codes are read by jumping the T1 and E2 connector on the diagnostic port under the hood, and reading the flashes on the 'check engine' light on the dash with the ignition switch in the 'run' position. Do not start the car.
The codes are for a fault in the circuit, not necessarily a bad sensor. Find a good Toyota mechanic in your area, and let him look at it. Both sensors are not expensive for this car if they do need to be replaced. If the Oxygen (O2) sensor was never replaced, or been past 5 years, it probably needs to be. A good Toyota mechanic will first look for proper operation of these sensors before replacing them. This repair should not cost you an arm and a leg. It should be a reasonable charge, as both sensors are easy to get to and check.
The car will not die. If the signal from either of these sensors fails, the computer will compensate by using a 'default' mode that will reduce your gas mileage, and increase the emissions to prevent damage from happening. Of course, in the long term, damage can still happen. Best to get it fixed.