A certain form in our application displays a graphical view of a model. The user can, amongst loads of other stuff, initiate a transformation of the model that can take quit
If you decide going with Threads, which I also find somewhat complex the way they are implemented in Delphi, I would recommend the OmniThreadLibrary by Primož Gabrijelčič or Gabr as he is known here at Stack Overflow.
It is the simplest to use threading library I know of. Gabr writes great stuff.