I have a Maytag Performa washing machine that has recently started giving me trouble with not shutting off the water when done filling and sometimes when going through the rinse cycle. What part needs repair or replacement?:

There are a couple of things that can cause this and yes the pressure switch is one of them. Your problem appears to be intermittent so I am not willing to condemn any part yet. Before we start throwing parts at the machine let's start at the beginning of the possible causes list.

Poor pressure or debris can cause the water valve not to seat properly.
To check, shut off the valves to the washer and turn on the washer to release the pressure in the hoses. Remove the hoses from both the supply and the valve. Check for debris in the screens. Reinstall the hoses on the plumbing side and put them both in the tub of the washer. Hold the hose and turn it on fully and then off and repeat for the other hose. Both should have similar pressue. Reinstall on the back of the machine and turn the water back on.

Debris, a kink or a hole in the pressure hose can cause it to not provide correct information to the pressure switch.
Depending on your cabinet you will either remove the 2 screws at the bottom of the front panel, tilt out and remove the panel and then remove the screws holding the top down. Or you will have pressure clips at the front corners you will press in with a putty knife to pop the top up. Your control panel will have screws across the top you remove and the panel will rock forward.
Rock the control panel forward examine the pressure switch hose in the panel. This time of year is the time for mice. This is one of their favorite places to take up housekeeping. Anything that isn't clearly machine parts doesn't belong in there. Lift the main top and follow the hose to the tub.
If you have a clear hose that goes to the left of the tub follow it down and verify it is connected. Now remove it (pulls off) and inspect for debris or a kink in the hose. Blow into it. Yo should feel the resistance of the pressure switch and it should not allow you to blow any additional air in. Re attach it and remove the hose from the pressure switch end and blow in it from there. You should have no resistance.
If you have a black hose that goes to the right you will need to unclamp it and remove it. Look inside of the large end of the hose you just removed is there gunk in there? If so dig it all out of the hose and from the hole on the tub. Remove the hose from the pressure switch and blow from that end to verify all the gunk is gone. Reassemble.

If all of the above things check good then I would replace the pressure switch.

If you need more help let me know.

There are a couple of things that can cause this and yes the pressure switch is one of them. Your problem appears to be intermittent so I am not willing to condemn any part yet. Before we start throwing parts at the machine let's start at the beginning of the possible causes list.

Poor pressure or debris can cause the water valve not to seat properly.
To check, shut off the valves to the washer and turn on the washer to release the pressure in the hoses. Remove the hoses from both the supply and the valve. Check for debris in the screens. Reinstall the hoses on the plumbing side and put them both in the tub of the washer. Hold the hose and turn it on fully and then off and repeat for the other hose. Both should have similar pressue. Reinstall on the back of the machine and turn the water back on.

Debris, a kink or a hole in the pressure hose can cause it to not provide correct information to the pressure switch.
Depending on your cabinet you will either remove the 2 screws at the bottom of the front panel, tilt out and remove the panel and then remove the screws holding the top down. Or you will have pressure clips at the front corners you will press in with a putty knife to pop the top up. Your control panel will have screws across the top you remove and the panel will rock forward.
Rock the control panel forward examine the pressure switch hose in the panel. This time of year is the time for mice. This is one of their favorite places to take up housekeeping. Anything that isn't clearly machine parts doesn't belong in there. Lift the main top and follow the hose to the tub.
If you have a clear hose that goes to the left of the tub follow it down and verify it is connected. Now remove it (pulls off) and inspect for debris or a kink in the hose. Blow into it. Yo should feel the resistance of the pressure switch and it should not allow you to blow any additional air in. Re attach it and remove the hose from the pressure switch end and blow in it from there. You should have no resistance.
If you have a black hose that goes to the right you will need to unclamp it and remove it. Look inside of the large end of the hose you just removed is there gunk in there? If so dig it all out of the hose and from the hole on the tub. Remove the hose from the pressure switch and blow from that end to verify all the gunk is gone. Reassemble.

If all of the above things check good then I would replace the pressure switch.

If you need more help let me know.