I installed my current dish washer. It just slid in. It was pretty tight, but it fit. I think the old one had more clearance on the opening. The new one just barely fit.
I was going to pay for installation, but the price for that has gone up. If your connections are set up right, it only takes a few hours at most.
Most home appliances are not all that hard to install if you don't have to modify the connections. Biggest issue is if you don't know why certain things are the way they are, you might not set up or connect something that should be there. In an old house, I forgot to knock out the blank on my garbage disposal for the dishwasher drain when I replaced the disposal. Never knew why the dishwasher didn't work. Realized it after replacing the dishwasher before I sold that house.