How we replaced the combustion blower on our furnace...

The shaft was bent too, so it was basically a big, ugly paperweight.  I contacted Dave at Furnaceparts.com and he sent us a new one without an argument, and it arrived a few days later (meanwhile my husband was out of town and the weather was chilly, so I kept my fingers crossed that the motor we had would hold out till we could get it fixed). 

Finally it was time to get to work.

First and most important step: CUTOFF POWER TO THE FURNACE AT THE CIRCUIT BOX.  I was tempted to just flip the switch next to our furnace, but my husband and electrical guru explained that occasionally a switch is miswired, and when it is in the off position, instead of having a very low voltage, it can have a very high voltage, so go ahead and make the trek to the circuit box, it may save you from getting zapped or worse. 

Here was our original (dying) motor:
The motor is actually contained in the black squirrel-cage (you can see the copper windings), but the part we replaced included both the motor and the nautilus-shaped blower to which it's mounted.   The blower sucks air in through a hole in its back, opposite the motor, and then blows it out through the circular duct at the top when the motor turns.   

I began removing the old motor by cutting the black and white (?) wires, and disconnecting the red rubber hose from the old motor (it pulled right off).  Then I removed the screws attaching the blower to the ductwork and the screws holding it in place.  It came out easily, and this is what we saw:
When we removed the motor we found a new part:
This gasket was in between the motor and the hole in the furnace, and was covered in fiberglass.  Luckily the new blower came with new adhesive fiberlass rings.
So I scraped off the old and stuck on the new. 

Next was the tricky maneuver of getting the blower in place while holding the gasket in place until the screws were tight enough to hold it for me.  Nothing complicated, just a situation where it was nice to have a third hand (from my husband.)  The blower is supported by  4 screws, and I put them in loosely at first and then gradually tightened them, trying to keep them all about even, to try to get a tight seal against the gasket.

While I was dealing with the gasket, my husband helpfully prepared the furnace's wires to power the new motor.  He stripped off a little insulation and crimped on connectors called FASTON tabs.  Once they were in place, it was easy to slide them onto the motor's terminals (it doesn't matter which wire goes on which side).  After taking the picture, I connected the red rubber hose to the nipple on the left.

Next I started to connect the ducts to the blower.  This required drilling holes to receive the screws.
Unfortunately the bit was too small the first time, which became apparent when the head of the first screw broke off.
But once the holes were redrilled, the remaining screws went in fine.  We replaced the cover, turned the furnace back on, and enjoyed the knowledge that we'd done the job for $126 and about an hour of our time.

A disclaimer:  This is not a "how-to" post.  It's a "what-I-did" post.  I'm not an HVAC technician, just a cheap homeowner.