Toyota Repair: 2000 Toyota Sienna LE, o2 sensors, fuel mileage

Question
I have a 2000 Toyota Sienna LE.  It has about 110,000 miles on it.  The check engine light is on.  The codes are P0125, P1130, and P1135.  I think these mean I need to replace o2 sensors.  Is there any way to tell which ones?  Hopefully not all three!  Could something else be causing these codes?  The van runs fine, and fuel mileage has not dropped off.  Thanks for your help.

Answer
You can ignore the PO125 code because it is a direct result of the other two, both of these codes refer to a malfunction with the #1 O2 sensors on both the right and left bank so my recommendation would be to replace both the bank 1,sensor 1 and bank 2 sensor 1, they are both located in the exhaust manifold.