Our few year old kitchen aid has been a nightmare of broken plastic internal parts. I will weep when my mother passes, but I will be taking her mixer and ditching mine.
You'll need digital calipers as well. You can cheap out for $20, or get Mitutoyo's for $200.
A scanner's also nice in scanning a geometry thats flat, but not required.
Just with a 3d printer and a meager ket, you can replace most current commercial crap in a few hours, and have the replacement as a file you can call on any time.
That's how I'm handling this "throw away culture" shit. I'm replicating what I need and throwing away the actual broken bits.
Reduce, Reuse, REPAIR, Recycle. (Hint: the manufacturers want you to forget the 4th, hidden R.)
It’s not deliberate that they make stuff that fails, they build stuff that lasts only as long as it needs.
KitchenAid switched to all-metal gears on their high-end models fairly recently. In the past, all models had a nylon gear, but the new high-end mixers use electronics to protect the motor.
TL;DR: The Pro Line is what you want. These have higher-wattage motors and are made with all-stainless steel. This is important if you mix heavy things like doughs or meats frequently, as these materials tend to stress and shear plastic more easily.