How to change the spark plugs andfuel filter in a

There isn't one.
What testing have you done?
Make sure battery has a full charge. If it cranks good but won't start, have a helper crank it while you visually check for spark at the plugs. If spark everywhere, use a gage and check proper fuel pressure and fuel injector pulse. If your missing everything check for rpm signal. Any applicable trouble codes?
When you first turn on the key, no crank, can you hear the fuel pump run for a couple seconds? There is a fuel pump fuse in underhood fuse box.

You can reset it with the battery for 30s just remove the negative plug

Chevrolet Cobalt 2005

Get your car fix right now :))

FIVE EIGHTHS SOCKET

change the cap

does it have gas? do you have spark to the spark plugs. are there any codes

check vacume hoses and check that all the intake parts are secure from the air filter to the engine

change your air and, fuel filters.

Number three cylinder is miss fire,it does not mean it is the coil,although it could be,remove the coil,and boot,and spark plug,inspect them to see if the plug,or boot look bad,replace the spark plug,and if the boot is burned or distorted,replace it,a fuel injector can cause a miss fire also,but change the spark plug and see if this solves the problem,if not replace the coil,if it is a dead miss,then the coil might be bad,as for the water in the fuel ,the cap is missing,,and 5 dollars worth of HEET will not hurt,also,fuel from the fuel station,can have water in it.It happens a lot.

It sounds like you have a fuel issue or spark issue. Pull your spark plugs and see how they look. If they look fine then test the fuel pump. You could try to run to fuel system cleaner through the fuel system and see if there is an improvement in idle. Could be any of the following problems,

coil
spark plugs
spark plug wires
fuel filter
fuel pump
injectors
air filter

Check the easy stuff like plugs, wires fuel pump and air filter first.