I have an old (75 yrs?) furnace (Colonial type 0, Green Foundry, Des Moines, IA). The sheet metal surrounding the firebox has popped off the base. Air from the blower now comes out this area and also through the wood feed door along with considerable smoke.The chimney is open and clear. There is no sign of a break in the fire box. Where might I get a diagram of such a stove and can anyone give suggestions as to what to do to repair the problem? Thank you.