My truck only has the single battery setup. I think I found one of the very few LN130 Surfs that only shipped with one batter. Accordingly, I've got a red-top Optima in it to give it all the help I can.
I have had ZERO problems starting in the cold. I've started it as low as -40C without plugging the block heater in. I'd hardly bat an eye at -20C.
But a block heater is a definitely good thing to install, even if they are a pain. You have to remove the starter on the 2LT-E to install it, but it sure is nice to know that your engine is already somewhat warm before you crank it--just for the sake of the oil seals and stuff.
As to the other questions.... I'm not sure about in Canada or Calgary, but I'd guess that any local importer would have a good answer. I use CDan, and if he can't get it, I go to Castle Hill Toyota in Australia. They've been great to deal with.
If/when the head fails, I'll order mine from Castle Hill Toyota if CDan can't get one here in the U.S. Any competent shop should be able to do the work of replacing the head, as it's no different than any other head replacement out there. I'll replace mine myself though, as long as I can get the truck back to my shop.
Your mostly city driving seems like it should help out the head longevity issue a bit--as you aren't going to be driving with the turbo spooled up for long periods getting the engine real hot. If you've never driven a third generation mini in the snow, then you don't know how sure footed they are. Decent tires and you're in fantastic shape. I've never, ever been stuck in mine (and I see a LOT more mountains than most).
The stock surf you're looking at isn't good for hardcore off roading. But it is excellent for an awful lot of really rough trails, if it comes to it. So while you won't be doing the Rubicon in it that way, you will also be able to go just about anywhere than the average *eep goes.
Dan