The converter(s) are located in the exhaust right after the headers. Note that it is illegal to tamper with your vehicle's emissions systems, and that included altering or removing the cats.
If the engine in that Mustang is maintained properly the catalytic convertor should last the lifetime of the vehicle.
The 2005 Ford Expedition 5.41 has two Oxygen Sensors that might need to be replaced at the same time. One is located in on the motor near the front of the catalytic convertor. The other O2 sensor is located behind the catalytic convertor. To change them, it is possible to manipulate the clips holding them in and remove them, then put the new ones in.
The fuel pump is located in the fuel tank
They are located before and after the catalytic converters in the exhaust system.
Absolutely not. The catalytic converter is an integral part of the fuel management system on your car or truck. The exhaust gases are measured before and after they pass through the convertor and the engine computer adjusts the fuel/air mixture to provide maximum power and fuel economy. Also it is illegal to remove the catalytic convertor and the fines if you are caught removing it or operating without it are pretty heavy.
The oxygen sensors in a 2005 Chevy Malibu are in the exhaust system. You'll find them at the end of the down pipes and behind the catalytic converter.
In the fuel tank mounted on the fuel pump
The oxygen sensor is located in the exhaust system on a 2005 Dodge Durango Hemi 5.7. There is a sensor located before and after the catalytic converter.
On the catalytic converter
Under the vehicle, in the exhaust flow, before the muffler.
Where did you get the leaded gas that clogged up the catalytic convertor? When was the last time you cleaned the gunk out of the fuel injectors? How many miles does it have on it and have you maintained it according to the owners manual?
2002 mustang models do not have cabin air filters. 2005+ models do have them, they are located under the passenger side cowl.