Oh yeh, I just read jerry S's reply, and you won't pay import duty, just GST. Import duty I believe is for cars under 15 years, something like that.
EDIT: I just re-read jerry's reply, and see said what I was thinking. Although, I don't think there is a duty on old cars, just GST. I think if you import a newer car, under that 30 or 15 or whatever year limit you pay the import tax, but not GST, but if it is older, no import, but GST.