I think Moe if you find out what color's are what in EU and you just look inside the breaker panel you will see it's a easy job. It's more like permanently connecting a extension cord to the breaker box really.
You don't need to worry about getting fried because you just flip you main switch when your ready for a minute or two to shut down all power and you just snap the new breaker in and connect the three power, ground, and nuetral to the breaker.
Just make sure you run the main power to your sub panel first and have it connected to that new 60amp sub panel breaker also in the off position. So once you flip the power back on its all connected and ready to be flipped. Just run your new outlets and wires, snap in the 20amp breaker's and flip the sub panel breaker.