On schedule as always, iFixit has documented teardowns of the new Mac mini and MacBook Air and given them each a repairability score. The Mac mini is an improvement over the 2014 model in a few ways. The MacBook Air has some positive points for user serviceability, but it requires a significant teardown to do much.
Starting with the Mac mini, iFixit found that after opening the enclosure, you just have to unscrew and remove the fan to get inside. The logic board can be removed without special tools. Unlike the 2014 Mac mini’s RAM, the RAM in this model can be replaced. It’s covered by a metal cage, but once you unscrew and remove that, it’s easy. The power supply can also be removed and replaced, but you’ll want to use a tool for it. On the negative side, the CPU cannot be replaced, and damage to any of the ports would require a logic board replacement.