Sewage ejector pump application

I live in a home that is approximatley 50 years old. Whenever ther is a large ammount of rain, the sewage system backs up into my basement. The previous owner installed a sewage shut off valve. This is somewhat nice, except you must be home and know when you basement is taking on water then manually close the valve. I have been told that all I need to do is install a sewage ejector pump, and pump any sewage that backs up into my basement out my front yard. Is this a proper use for a sewage pump? If so, how do I know what size pump to purchase? This seems like an easy enough job to perform myself (almost too easy), however to be on the safe side can anyone supply me with instructions on doing this? Thank you. Bob