1999 Hyundai Accent O2 sensor

How do I replace sensor number two on the car, it appears to be the one down stream form the converter, I had the diagnostic scan done and came up with fault code P0136 and I think this is the sensor located in the exhaust pipe. Can I replace it without going to a lot of extremes. The engine is this car is a 1.5 lLiter SOHC . Th car has about 76000 miles on it.

also if I do replace the sensor myself do I have to have the computer reset or is there a trick to resetting the computer without going to the parts store and resetting with the scanner.