2000 Buick Century question on codes?

Wife came home from the car repair place and they had changed the throttle postion sensor. And also gave her these codes and said they need to be fixed
1. PO137 B1 Sensor 2
2. PO141 O2 Heater Code
3. PO300 Miss Fire Code
4. Fuel Tank Pressure Sensor
Can anyone tell me what these mean, what i need to do to repair them and where they are located at.

Mike

atacking multiple codes is a problem clear them all and address the first one to come back first then your not chasing ghosts

P0137- low voltage, post-catalytic converter oxygen sensor
p0141- heater circuit malfunction, post-catalytic converter oxygen sensor
p0300- random cylinder misfires

the first two looks like it's time for a post-converter O2 sensor. If you've had the common intake gasket failure on this car, the converter itself could be plugged with coolant residue which could cause the p0137 and p0300 codes, but not the p0141.

the fuel pressure sensor code could be the sensor itself, something as simple as a loose, leaking gas cap or something harder to track down like a cracked/broken plastic line anywhere in the evaporative emissions system.

Thank you both for your help and input! I replaced both O2 sensors yesterday and reset the computer. We will drive it and see if anymore codes pop up and go from there.

Mike