Toyota: '84 Corolla Diesel--advice needed

Can anyone advise me of the viability of this vehicle--especially the
engine? It has about 100 K miles on it and runs poorly.

I have some familiarity with Diesels but these light duty timing-belt
things are our of my experience.

Are parts, and service information, readily available for this engine?
How well do they hold up? How long do they last...?

What goes wrong with them?

Thanks,

am