whirlpool gold 1200 will not spray

When I choose the normal cycle, the dishwasher kicks in (no apparent error lights / indications) and starts filling (an inch or two of hot water at the bottom), but when it hits the wash cycle, I just hear a humm.
The water drains fine. All was working fine a week or so ago.
Any ideas would be appreciated. I'm kind of assuming a pump has seized up. If that's the case, how difficult is it for the "average guy" to replace.
Thanks.