The house we bought in the past year has a crappy-a$$ dishwasher that I would love to replace, but I am not interested in spending any real money to replace it at the moment. The dishwasher's transgressions are as follows.
It has about half the capacity of my parents' (admittedly $$, fancy) dishwasher
If I put so much as an extra plate in, it leaves some dishes not quite clean
It is LOUD. That wouldn't be that big of a deal except it cries and whines and moans and happens to sound just like my baby crying i the next room. We find ourselves constantly asking each other "is that the baby crying or the dishwasher?".
So my question to you smart people has to do with how to go about finding a replacement. Are all dishwashers the same form factor? Meaning, do I need to worry about external dimensions fitting under my counter, or is that all standard? Same question for hookups behind the dishwasher itself. Aside from looking up model numbers on Consumer Reports, is there any general advice for how to find something that will do a better job than what I currently have? I'm a little wary of the fact that it will require a good amount of work to uninstall the existing one, install a different one, and then run a load before I will know how well a replacement will perform.
Dishwashers are not all the same size. You'll have to verify the height, width and depth. The removal and installation is very easy (can be done in about an hour) unless someone hacked the original in there without a breather or other crap. The hardest part (annoying, not hard to do) is fiddling with the leveling if your floor is not level under the cabinet. This is pretty common as often builders will only install subfloor/vinyl/tile part way under the cabinets. If you are reasonably handy with a pipe wrench, level, a screwdriver and basic wiring you will have no problem and save yourself a bloated installation fee.
Decent new entry level dishwashers are cheap ($300 before discounts); don't mess around with used items. It won't be super quiet or have spendy pants options but it won't be as likely to leak or fail, and will have a warranty. And if you buy new most stores will take your old unit off your hands free of charge. It's really not worth the hassle to deal with used; water damage can get very, very expensive to fix. The only exception would be someone doing a remodel or similar who is getting rid of a high end washer (<2 years old) old for aesthetic reasons.
Also check your state and locality for tax rebates for installing energy efficient appliances.
Finally, regardless of your choice of used or new, do NOT try to reuse the existing supply hose (neither your existing or whatever comes with any used item you might get). This is just asking for trouble. Always, always replace these when replacing the unit, and replace them every 3-4 years even if you aren't replacing the dishwasher! Use the steal braided hoses. This applies to dishwashers, washing machines or anything else with a pressured supply hose.