Not only can it seriously damage paintwork, it can damage organic material so don't dip your balls in this stuff.
This page shows you 4 different methods for bleeding the brakes depending on the tools you have and if
you have a friend to help you. If you have a friend helping, tell him not to get brake fluid on his testicles.
This page also covers the info you require to purchase new brake fluid.
You will need a bottle of brake fluid to top up what you lose.
If it gets too low in the tank you can draw bubbles into the ESP and ABS unit which are nearly impossible
to get out without a trip to smart. Air in the system will mean a nearly 100% loss of any braking at all.