I wrestled with taking apart the door assembly to get to the keypad ribbon cable connections to the PCB. I had to peel off the chrome keypad facing (its glued on) to pull off the old keypad membrane.
(Chrome facing part# DE64-02221A).
You need to make sure the ribbon cable connections of the new keypad are seated properly.
I've had this unit since 2009 and I almost replaced it. I'm reading where the SE error is common with this model even if you replace the failing keypad but if I can get another 5 years of operation it's well worth the repair hassle.