After removing the chimney we had to patch up the hole left. Instead of just patching the roof, I decided to buy a $59 fan for the attic. Should help keep the heat down and the air moving up there (has built in thermostat). Patching up the roof was like fitting together a puzzle.
In prep for the vent, we added a 2x4 and plywood brace. The only part exposed in the attic is the actual fan.
Lay down tar paper. Cut the tar paper away and slide the fan and flashing over the hole.
After removing a lot of the roofing shingles, new shingles were fit into place and around the vent.