If the plug-ins are corroded enough where you're having trouble getting them apart you prolly need new connections. With no power in the circuit try a penetrating oil(spray) like PB Blaster etc to get them ungunked enough to get them apart w/o breaking them. Spray them well with an electrical contact cleaner and see how they come out. If they're salvageable smear them with dielectic(sp?) grease before putting them back together. That'll keep future water out of the connections. All the above are available at any auto parts store.