Diplomat APL 8225 dishwasher not washing

My Diplomat APL8225 dishwasher won’t wash. It fills & empties but the washer/circulation pump won’t pump. It makes a humming noise when it should be pumping and the pump body gets warm but it aint pumping. I’ve had the motor out & it will turn but it’s very stiff (should it be stiff to turn?). I think I prob need a new motor but just want some confirmation before I go & buy one. Is there any other fault that would cause this to happen please. And where is the best/cheapest place to get a new motor?? Thank you.