Disassembled keyboard and mouse:
Scrubbed plastic, rubber feet, cables and mouse ball with toothbrush and toothpaste and reassembled once thoroughly dry:
I've come to the conclusion that there's not much point doing this mod if I change the external appearance of the machine too much. I think the angular mouse, the bar at the back of the keyboard where the reset switch is and the coiled keyboard cable and perhaps the mouse cable joining to the keyboard are a key part of the style. So I want to retain these features.
The keyboard doesn't have the full complement of normal keys for a PC though and the mouse has just one button. There is also the ADB protocol issue.
I've considered replacing the mouse electronics with those of a modern mouse and cutting the one button in half with a hole for a scroll wheel which might work quite well. I've also thought about cutting up the keyboard shell and wrapping a modern keyboard with it which is going to be more difficult to get to look right owing to the different keyboard layout.
There are also ADB to USB converters on the market but they are expensive and I don't know if they solve the problem of missing function keys.
So, for the time being, my plan is to use a microcontroller to translate the ADB signals to PS/2 and keep the mouse and keyboard unmodified. If necessary, I can use the microcontroller to translate key combinations to get the missing keys. This is going to require a fair amount of effort though so it's only going to be worth doing if the rest of the mod turns out well.
The next big problem for aesthetics is the screen. Again, I considered modifying the face of the machine to fit the LCD panel better, either by milling the aperture or by cutting the case in half vertically and horizontally and stretching the whole case to fit but the curvature of the face will interfere in both cases.
It turns out that if I can configure the display to show 1920x1440 centred on the 2048x1536 panel with black borders then the display area will almost exactly fit the aperture. I need to wait until I have the displayport adapter for the panel to test this.