Over time soot builds up on the rotating electrical pieces - this makes sparks and more soot. 28 years is impressive...
It will probably benefit from an overhaul - new brushes - clean the commutator - clean up the centrifugal speed control which will also have dirty and sooty contacts.
If it has a motor capacitor then that may well be a cause of the smoke - capacitors do not last forever.
All this is in the capacity of a handyman with a few hand tools and a little confidence.
To pay somebody to do it for you would probably not be cost effective - your realistic options are...
Do it yourself
Have a friend do it for you
Buy a new machine