THE PLT WAS BRIEFED ON THE WX BEFORE DEPARTING WAUKEGAN, IL. AT THE DESTINATION, WOODRUFF, WI, THE WX WAS FORECASTED TO BE VFR, EXCEPT FOR LIGHT RAIN & THE CHANCE OF SCATTERED THUNDERSTORMS. WHILE EN ROUTE, THE PLT CHECKED ON THE WX & SPOKE WITH ANOTHER PLT THAT HAD JUST FLOWN ALONG HER INTENDED ROUTE. THE DESTINATION ARPT REMAINED VFR AS FORECASTED. BEFORE ARRIVAL, THE ACFT ENTERED CLOUDS & PROCEEDED INTO AN AREA OF THUNDERSTORMS. THE PLT REPORTED HER RADAR WAS PAINTING HEAVY CELLS OVER THE ARPT & IN ALL DIRECTIONS, THEN STARTED TO DIVERT. SHORTLY AFTER REVERSING COURSE, THE ACFT ENCOUNTERED A STRONG DOWNDRAFT. THE PLT ADDED POWER & RAISED THE NOSE. SHE REPORTED 'WE WERE PULLED UP INTO A STALL.' AT THIS POINT, THE ACFT ENTERED A NEAR VERTICAL DIVE. DURING RECOVERY, THE LEFT WING HIT A TREE, BUT THE ACFT CONTINUED TO FLY. BY THEN, THE ACFT WAS OUT OF THE CLOUDS & THE PLT FLEW TO THE ORIGINAL DESTINATION & LANDED. DURING THE LANDING, THE LEFT GEAR WAS 'SHUTTERING.' THE ACFT THEN BEGAN TO SKID, WENT OFF RWY & THE LEFT GEAR FAILED.