It may be the motor or it may be something simple like a fuse, you need to test for a voltage at the heater motor using a test lamp or volt meter.
You should be able to see the wires going into the heater fan by looking up under the passenger footwell.
You will see the two wires going into the heater fan, and if you can test for a voltage that will either confirm it is the motor, or if there is no voltage this will indicate another problem.
Have you checked the fuse? this is number 5 in the engine bay fuse box.
As it is the blower that is at fault, this should not be connected to the juddering you have, the most likely cause of this may be worn fuel injectors and this may also be connected to the smoke you see on start up
I hope this answers your question but do please ask if you need further advice.
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