Could be something caught in the drain pump or the pump could have simply failed and needs to be replaced.

That maybe best if it's full of water and you have never changed one before.

I suck out what water I can with a shop vac after removing the spray arm and covers. The reach in through the access panel and change it. Good way to scratch up your hands, but it gets me in and out the door and on to the next call faster. ;)

You don't need to do anything from inside the dishwasher. The only reason to be inside the dishwasher is to get the water out.

The drain pump has to be changed from the bottom of the dishwasher.
You would be best to pull it out and lay it on it's back so you can see what your doing.

The pump just twist on and off the sump housing. There is a plastic tab that keeps it locked in place, no screws.

Really simple once you can see how it is.

I changed the drain pump this evening. Went in through the access panel. Thanks to some You Tube videos it wasn't too bad. But when I put everything back together it still isn't draining.

When I removed the old pump two of the impeller blades were missing. There had been a grinding noise for a week or so when the drain cycle was running. My guess is that the missing blades are stuck in the motor somewhere. Is it feasible to take apart the motor to a point where I can maybe remove the stuck blades or should I replace the motor?