I hav chg spark plugs,wires,low coolant,service engine light won't go away.

Remove it! Pretty straight foward to see how, couple of screws then disconnect hose(s) pull up on it. Replace sensor or the tank assembly.

seek help from your mech

Have vehicle scanned for codes. The low coolant light may not be related to the service engine light at all. Try taking a rubber mallet or hammer and tapping on the overflow tank (not too hard) around the sensor and see if it will unstick itself.