Is the only difference the currency, or are you doing different language? Do you want to do it based on an exchange rate? That might be easier than redoing the entire site. You could have the .com go to the same IP address as the .ca and use all of the current site and just adjust prices. I'd probably go that route if possible if you aren't doing an entirely new language.
If you wanted a different price (not based on exchange rate) then you could also just add one more field to the products table to store it and not need to copy the entire site. I'd strongly suggest using a single code base if possible since it will save you a lot of headache in the long run.
I could help you set up either technique in a premier support ticket.