On the concern of replacing an 18" dishwasher if it fails - I see a variety of brands and models from a variety of retailers that are available within the week. The 18" size is not standard but it is also not so rare that I think replacement would be a concern.
I’m sure this will change when I get used to it, but I see a dishwasher as a luxury, I don’t think I’ll be too upset if I have to wash dishes for one week.
I think my main concern is really limited to whether the size is large enough and whether the machines available are of an acceptable quality.