To answer both of your questions, the potential damage would probably be of little concern, most likely it will create auroras at the poles and not
much else.
However it has the potential to interfere with satellites and signals and even effect the electricity grids on Earth among other things. But these are
not common and until further information comes in there is no need to panic. It is unlikely it will effect our day to day lives. Don't hold me to
that though
You should be fine to leave your electronics on, but of course you don't have to.
Hopefully we can keep this updated, and others can add their information too as they find it. I am no expert by any means, just sharing the info as i
found it.
There is roughly 2 or 3 days before the charged particles arrive so that's when a lot more info will come in i imagine.
[edit on 14-3-2010 by pazcat]