Dishwasher will work, just will not drain.

My wife had noticed that the dishwasher had water still in it after a wash, so I told her to put it thru the rinse cylce to see if would drain. It did not. Should I change the whole pump and everything or just go with the kit they sell? I would hate to pull it all apart, change the kit and find it is the pump. Please let me know what you guys think.