GE Range Oven temp not accurate and Timer unreliable

[JRA]

Model Number: JGB750EEF1ES
Brand: GE
Age: 6-10 years

The oven has an approximate drift of 40 Degrees. With a Set point of 300 it drops to 185 and climbs to 325 Deg. Also the Timer is unreliable and sometimes does not work suspect the main control board going bad. Any ideas??