Kittys,
The smoking motor indicates it's full of dust, dirt, and lube that migrated to the armature.
Scratch that local sewing machine shop off your list and do it yourself. Don't trust your machine(s) to them.
"
CAREFULLY" ( they can be replaced, but it's best not to break them ) remove the motor brush caps then work the brushes out of their tubes. Clean them, the tubes and the armature with a q-tip soaked in denatured alcohol to get the old lube off.
If the brushes are too worn out, ( I've read they should be longer than they are square for best function ), you can get new ones at Sew-Classic.
Inspect the wiring while your there and lube the motor. Use only the old amber Singer Motor Lube in the tube if you can find some, or petroleum jelly. Don't over do it, but it's been sitting so it will need some.
Once the motor is cleaned and lubed, remove the belt and run it wide open till it cleans itself off. I doubt it will catch fire, but it will probably smoke for a while.
When it gets warm add a bit more Motor Lube to the ports and then run it some more.
That should take care of the motor.
Then clean and oil the entire machine. Use Singer gear grease ( the white stuff they sell now or better yet Tri-Flow grease) for the gears under the spool peg plate.
After that she should be good to go.
OK, here's some info to study up on:
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http://www.quiltingboard.com/vintage...t-t221641.html }
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http://www.quiltingboard.com/vintage...t-t174236.html }
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http://www.quiltingboard.com/vintage...s-t193635.html }
I recommend Tri-Flow oil and grease for everything but the motor. For the motor I use only the old style Singer Motor Lube in the Tube, if you can still get it. If not then go to petroleum jelly. Supposedly the Singer Lube and petroleum jelly is indistinguishable from each other.
Joe