Thanks for all of the advice, I removed the old machine last night. It took 3+ hours but I eventually won the battle!
The dishwasher box is formed of flimsy steel, but it has heavier structural steel framing around the front and back. The front was accessible, so fairly easy to cut out, but the back was difficult due to it's position inside the cavity. The sawzall was either hitting the cabinets/counter, or not penetrating deep enough, which violently ejects the saw from the cut. Fun! Maybe I need a sawzall lesson.
So, I'm picking up a new water supply line and fitting today, and fingers crossed, I will slide the new machine in and hook it up (we purchased the machine last week).
The installation guide specifies a 34" opening height requirement, my opening is 33 1/4".
The new machine has plastic wheels on the back. If necessary, I believe that I can remove the wheels for an additional 1/4" of clearance, then I'll figure out how to shim it from there if necessary. This still leaves me a half-inch of problem, but hopefully they included some wiggle room in the spec.
If there is a lot of wiggle room with the new machine, I'll also consider raising up the floor under the machine to match the cosmetic floor. That will simplify future maintenance.
I guess the former homeowner is ultimately accountable, but he probably just had someone perform some renovation tasks and never thought about the DW implication. The counter and/or flooring installers should have raised this concern. Maybe they did, and he ignored it.
Hopefully I'll add one more happy post tonight after I've started the machine's inaugural cycle.
Thanks again for you advice and insight.
Photos:
Floor height 3/4" (the counter top bullnose trim is also 3/4", even with the cutout):
Bullnose Trim: Upon further inspection, the bullnose edge
was already trimmed down, about 1/4" on the left, maybe 1/8" on the right. Worst-worst case scenario, I'll have someone come out and trim this further. I never even noticed the cutout before last night. Not visible in this poorly lit picture is the top of the
machine, which is slightly higher than the top of the
door (which is visible).
With the front reinforcement removed, the machine now slides 75% out of the cavity (then the back reinforcement get's jammed).
Trying to get back to the back reinforcement framing: