This is what has kept me from working on amps. I'm comfortable working inside of pedals (9v) or with USB-powered circuits, but anything with a large transformer just seems a lot scarier.
It depends on the "power" of the project. I was building ½ Watt Darling hi-fi amps that never had more than about 225 VDC or so running through them.
But by all means, you never touch it when plugged in, you use chopsticks if you need to poke/debug a live circuit (you keep one hand in your pocket, etc.).
225VDC will kill a person, but it entirely depends on the current that can be delivered. As little as 50mA can kill. Your 1/2 watt amp probably won't but I don't know the details of the power supply.
