Product review (5 stars): If you are handy, this will save you a bundle
If you are even sort of handy, you can install this kit.  You won't be looking at this unless you have already read up on what might be wrong with your dishwasher, so if this kit is indicated, order this, get out your tools, and prepare to delve deep into the guts of your dishwasher.  Watch this video a few times:  https://www.youtube.com/watch?v=-hS0v8uP09I

Now when the video says it may take considerable force to remove either of the impellers, believe them.  The first impeller you encounter may discourage you.  Mine started chipping away as I was trying to pry it loose.  Eventually, you will get it out.  The lower impeller was almost impossible.  A little research indicates even the pros often have to cut the thing off, which is what I did with a Dremel (purchased on Amazon.)

Once you get to the end of the disassembly and clean things up (all those chips, plastic dust from cutting, and try to clean up the motor shaft) all the new parts will go together very quickly.  The kit has all the seals you need, and maybe one extra, as well as the hard parts, so there shouldn't be any surprises.

I don't know what an appliance repair company would charge for the job, but I'm sure that if you are willing to invest a couple of hours and some sweat, you'll save a bundle.  The kit is genuine Whirlpool, so it's good stuff.