A celebration of more than 100 years of Mercy HS -- all friends of Mercy welcome. Begins with 4:30 Mass, followed by the ceremonial closing of the school's main entrance (building will be open for self-guided tours until 7 p.m.). Community dinner on the lawn  - hot dogs and hamburgers cooked by Mercy Dads (please bring a side or dessert dish to share -- bottled water and soda available for 50 cents; beer and wine available for $1). Pete Wagner…