Time to get started!

Welcome to FABO, great group here and you will find plenty of help/advice.

hope the coolant leak is in the radiator or hose and not a freeze-cracked block. aside from that, everything is pretty straightforward in the cooling system. make sure that the heater core is not leaking as well. check all hoses and both sides of radiator for leak.
the master cylinder is pretty easy, you will have to bleed the brakes once its done but for peace of mind and safety's sake it wouldn't be a bad idea to replace the entire braking system with new parts if you have the skills/$$$ to do so. its not that hard and should be the first thing anyone who attempts to work on cars should learn because its the system that you are betting your life on every time you start the car. upgrade to dual-chamber master cylinder if you don't already have one.
good luck and post some pics so we can see what you're working with.
-Tim