I seriously doubt there's an SMPS in any audio amplifier that's as life threatening as the big linear supplies resting in the heart of any class A amp
What's life threatening is high voltages. It only takes a few milliamps to stop your heart. I believe that switching power supplies have much higher peak voltages than linear amps of the same power. In the 200-300V range. The amplifier portion itself runs lower. This is all quite fuzzy and old knowledge so I can be wrong.
That thing takes nothing more than screwing boards into a box and running wires to a power switch and signal posts. I can't imagine it being more simple than that.
And this is also true. Assembly is dead simple. Keep your fingers and tools out of the way when it's on, and be aware the caps can maintain a very high voltage even after they are off.
Best,
E