It's health and safety, there's no problem taking the cover off if you have a bit of training and some tools. No one is going to encourage you to do it, especially not some random on the internet!
If I had the time I could describe a few ways that the process can go wrong but there are quite a few checks you should be making after the work which it sounds like you are not equipped for.
If you have any exterior fittings on your installation I would disconnect those. Switching off the breaker doesn't necessarily solve the problem of a line/neutral fault which is what the RCD is supposed to pick up because of the way the neutrals are joined in some cases.