That rice wasn't in there long,no oil was sopped up by it--I'd just vaccum out whats visible,drain the oil out,put the drain plug back in and dump a few gallons of diesel or kerosene in the crankcase,let it sit overnight or longer,and drain it out again...fill with fresh oil and fire it up--might want to spin it over with the coil wire off till it has oil pressure first,it'll help avoid a dry start..
Unless there is a few pounds of rice in the crankcase and the oil pump screen gets completely blocked,I doubt any harm will be done..it will get ground up and sent to the oil filter post haste,and its too soft to do any real damage..