To replace an oil and wood furnace, disconnect the stove pipe, clean the pipe, remove the hearth bolts, move the furnace out of its position, and then secure the new furnace. Wear gloves and a face mask to protect your hands and face from soot and debris, advises DoItYourself.com.
Begin by shutting off the furnace, including all electrical and gas connections. Double check the fuel compartment of the unit to make sure it is empty. Next, disconnect the stove pipe from the furnace. A screwdriver or wrench is typically sufficient to remove the connections and joints.
Clean the disconnected pipe of all soot, grime and dirt build-up. Avoid bending or molding the pipe in any way so it may be reused to reassemble the new furnace connection. Once the furnace is disconnected from the stove pipe, remove the hearth bolts so the furnace can be removed from its position. The furnace is heavy, so you may need another person to help remove it.
Purchase a new furnace of similar size. Be sure the new furnace has the capacity to heat the desired space. Place the new furnace in the same place as the old one, and secure the bolts to the hearth. Reattach the stove pipe, and verify that there are no leaks in the connections. Once the stove pipe is tightly sealed and attached, turn the furnace to the on position.