I am a shut off the circut breaker type of cautious person, though worker in my home always say turning off the switch is enough. For them maybe!!!
you just have to put the wires back in the same order they are designed to be. The new fixure should tell you what goes where.
It is helpful to hve someone to hold the fixture for you. Then you are not juggling the weight and the concentration on proper wiring.
Electricity scares the beejezus out of me, but I have done it. So yes, if I can, anyone can