The airport is eight miles from downtown. Immigration depends on time of day, how busy airport is etc but would say in all allow one and a half hours from arrival time and you should be ok. Taxi from airport no problems.
BTW kjn, we are staying at L'Hermitage, can you recommend a good restaurant nearby that we can probably walk to? It's hubby's birthday & we'd like to eat somewhere nice if possible but without having to go too far.
Q4 Centro in the hotel is an excellent Italian restaurant. Amazing food. Most restaurans close by all seem to be Italian. ( which suits me fine). If Italian is not liked then try Meat Poutine 718 Nelson Street for Canadian dishes. .Enjoy your trip.