Toyota Repair: 2003 Rav 4 a/f sensor, state emissions, system failure

Question
Ted,
My engine light went on.  The advisor @ Toyota said it would cost $110 and take a large part of the day to diagnose because some cars need reprogramming of the Fed emission parameters. If that is the case it he said it would be free, but if not then I would be credited the $110 towards the repair identified by the analysis.  Since I dont like flying blind, I got a free engine code reading from a local mechanic while he changed the oil.  He identified code p1135 a/f sensor heater circuit malfunction-Bank 1 Sensor 1 (code A - system failure).  

He quoted me a price of $230 for the part and $95 for labor ($348 total w/tax).  Funds are tight-this hurts.  

The vehicle has 73,000 miles on it and this light has been on for about 8000 miles.  It is an automatic and has 50 state emissions.  

I'd like to fix this myself. I have worked on cars - just the basics. Some Questions:

Is this code specific - requiring the replacement of the a/f sensor - or can the problem be something else trigering this code, but only a $110 Toyota complete diagnosis will expose the root cause?

How do I know if I should replace the a/f sensor?

This sensor is easily accesible- If it is the problem, and I were to replace it, are there any hints you can give about the process - i.e. what do I torque it down to, etc?

Autozone describes a few causes for this code - (The a/f sensor heater circuit, ground circuit, or heater power circuit is open, or the a/f sensor heater is damaged or has failed, or the PCM has failed.)

What is a PCM?

Does Toyota warrant this ever?

Sorry for the many Q's.  Thanks in advance for any help.
Tom

Answer
Yes that code is specific to the bank 1 sensor 1, this engine has for sensors in the manifold, two before the catalityc converters and two behind, both #1 sensors are the ones in front of the converter. The bank 1 sensor 1 is the one to the right(standing in front of the car) on top before the converter. There is a special socket required but you may be able to work around that by removing the heat shield first. The PCM or ECM stands for powertrain control module, engine control module, they both mean the same, it's the engine management computer. After replacing the a/f sensor the computer should be reprogrammed if applicable, check with the dealer if this needs to be done, the warranty period for that is 8yrs/80,000 miles.