DURING CRUISE AT 7000' MSL, THE PLT ASSUMED THAT HE WAS HAVING AN ELECTRICAL FAILURE BECAUSE HE HAD NOT HEARD ANY ARTCC TRANSMISSIONS, FUEL GAUGES WERE INDICATING LOW FUEL, AMMETER READING WAS ZERO, AND LANDING GEAR WOULD NOT CYCLE. HE SHUT OFF ALL ELECTRICAL EQUIPMENT EXCEPT COMM AND PROCEEDED TO SOUTH BEND AIRPORT. WHILE PREPARING TO LAND HE CHECKED THE POSITION OF THE OVERRIDE LEVER FOR THE AUTOMATIC EXTENSION OF THE LANDING GEAR, BUT DID NOT TRY TO RAISE AND THEN LOWER THE LEVER AS SUGGESTED UNDER EMERGENCY PROCEDURES IN THE ACFT MANUAL. PLT ALSO STATED HE DID NOT TRY TO YAW THE ACFT WHICH IS ALSO RECOMMENDED IN ACFT MANUAL FOR EMERGENCY GEAR EXTENSION. ALTHOUGH THE PLT DID TRY TO VERIFY ELECTRICAL FAILURE BY TURNING ON THE PITOT HEAT, HE DID NOT FOLLOW THE PROCEDURE TO SWITCH OFF THE ALTERNATOR FOR ONE SECOND AND THEN BACK ON TO SEE IF THE AMMETER CONTINUED TO INDICATE NO OUTPUT. ACFT LANDED GEAR UP RESULTING IN SUBSTANTIAL DAMAGE TO ACFT.