Suz, I'm glad to hear you're feeling more optimistic and less panicked about this by the time I'm getting to this thread.
As it happens, I panic every. single. time. I have to go on a trip (and the longest has been 10 days, usually more like 3-4 days, plus 2 days flying!) --- I have been doing this for the last 7 years, without fail, starting at best 2 weeks before the trip and more often a month in advance. Also, I just came back from a day's window shopping in the malls to declare I have LOTS to wear, as long as nothing is expected to remix or anything! If I can put every garment into ONE outfit that works for comfort, (my) style and practicality... I heave a huge sigh of relief! So I hear you *really* loud and clear!
That Vivienne Files exercise of 4x4s? Well I was all agog the moment she posted it, and tried EVERY colour in my wardrobe, even mixed colours (like Vix says)---and got nowhere. HAVE to buy with intention and focus or it does NOT do at all.
HOWEVER, all that said, I do manage to get to those trips and not be entirely uncomfortable. Yes, there are times I feel very self-conscious, and yes, I've been too cold on occasion or too old-fashioned or startlingly Indian (my secret weapon when all else fails!). BUT I haven't managed to shock anyone unduly, I trust.
So while I'm saying nothing that's not been said before piecemeal, seriously, start with the shoes and work upwards. Like Natalie says, use your favourite outfits as the basis of your suitcase and then, like Tanya said, add a few extra options (I add bottoms as well as tops --- for good reason, such as paranoia :-/ ). Do it with the next pair of shoes... and so on. I know it isn't ideal, but if you can take three pairs of shoes, do! There is no must-do 'fab travel rule' apart from be comfortable, be covered and be confident. (Well, there are, but travel is surprisingly easy to do even in disobedience of the 'great versatile capsule wardrobe in the sky where everything works with everything').
Once you're done packing, had a cup of tea/coffee or glass of wine and a slice of cake... figure out that 4x4 core colour you want to start with, and keep a weather eye out while abroad. You'll get there yet!
Hoping by tomorrow you're well sorted and no longer worrying about your wardrobe. It will 100% certainly be waiting patiently to get sorted out for the final time when you get back. Focus on that exciting Banff opportunity now!