Just so you know, you can add the B777 rating to your Canadian license without a large hassle. I did just that, cost $30 a few years back and they just needed to see the last few pages of your logbook to verify you were legitimately typed.
I realize this is separate from your IFR, but I wouldn't worry about that unless you're looking at working in Canada again in which case your new employer would take care of that anyway with your initial course...?
Not sure about the written exam part but it's not exactly hard anyway.