Try heating up the connection up first before trying to take the connection apart. There is a sealant that is used to prevent moisture from corroding the wire leas inside the connection, warming up the connection will cause the sealant to turn in to syrup like substance which makes the clip easier to come apart. http://userdata.expdatasol.com/TechChoiceParts.com/public/apcontent/Harness Connectors.jpg
Good luck and you don't need that much heat, a hair dryer will do and be safe.