Make a short length of mock-up molding to confirm the size/weight of the finished crown molding, and then purchase the stock baseboard, molding and other components. Assemble your tools and safety equipment. You will be working with power tools and creating saw dust, so be sure to wear safety glasses and a mask. The height of the ceilings will require standing on a ladder--using the right size ladder and bracing it for safety are standard operating procedures. Wear non-skid shoes that fit securely, preferably shoes that also have hard soles to save your feet from the distress of standing on the rungs of the ladder.