Creating and Maintaining a corvette club web site at http://gnocc.com/ and helping maintain a Geocaching website at http://louisianageocaching.org
Oh and helping out HERE!!! When I have time...........
WOW, at that price plus shipping and refrigerant , you are getting into the relm of replacing the whole unit. It is not worth trying to revive a R-22 system when the fix will be close to $1500. R-22 is being phased out and as such the price is getting higher every month. They will totally stop manufacturing it in 2020. It is already over $500 a drum on wholesale level. ( used to be $20 a drum a few years ago).
If you have access to affordable refrigerant, then go for it. otherwise consider a new 410a system.
Don't worry about the aluminum wiring. The worst thing that could happen in the future is the connection point in the new heater where the aluminum meets the internal copper wiring iwill burn up. since it is contained in a fireproof metal box( the air handler) ... The furnace simply stops working and someone has to cut back and reconnect the wires.
If the aluminum wiring connects to a screw type terminal block you have absolutly nothing to worry about. if the connection is a large wirenut ....It must have the special aluminum grease ( green stuff) to ensure a long life without worrying about burning up) . there is a problem when you connect aluminum to copper wire. it will degrade over time and heat up.
The large wires coming into most everyones homes have always been aluminum. when was the last time you heard of a problem with that? the wire going to the heater is also a very large aluminum wire. And it is multiple smaller wires twisted together. makes the wire very strong and very unlikly for anything to happen.
The problem comes with the smaller wire (12 and 14 gauge) to electical outlets. these single strand wires can degrade and heat up causeing a fire inside your wall.
End result ... your exsisting wire to the heater is ok. If she has aluminum in the walls....welllllll...that may be a probem.
due to the age of your furnace , before you invest ant money in a motor ......
You should thoroughly check the heat exchanger for cracks / rust holes .
Pull the blower assembly out and put a bright light in the burner section. When looking into the hole where the blower blows into , you should see no light. if you see any light , the heat exchanger is failed and funace must go.