That's great if you're already speaking Swiss German, it will make it so much easier!
I still remember making my first phone call in German (I speak a clumsy mix of High German and Swiss German and have somehow picked up a Dutch accent along the way?!) to book an optician's appointment. Not rocket science but it gave me a real confidence boost to have been understood!
Don't totally discount using englishforum.ch. Yes, there are some snippy responses but I've found it really useful and informative especially if you have a particular query. I even got a job after following a link someone posted there. I haven't used it much in the last couple of years (switched to MN after the birth of my daughter) but I remember they didn't particularly like vague questions such as 'can we survive in CH on a salary of 150,000CHF?' and they expect you to have at least tried the search function.
I use the C&C in Chur too :) It's good for large quantities of frozen meat and also for fruit and veg that you'll easily get in a British supermarket but are hard to find here sometimes especially out of season. Mange tout springs to mind!
As for nappies, after I got through the hundreds of Pampers my mum brought over for me I switched to Lidl's own brand and I find their sensitive wipes brilliant too- my DD suffers with eczema and these don't give her any problems.
Driving here is generally fine. The roads are a lot less congested (with the exception of the motorways around the major cities) and much better maintained than in the UK. When it does snow, they get it cleared quickly and you'll have winter tyres on your car anyway. There are 'snow-driving' courses you can take to make you more confident and if you don't want to risk it then you can pretty much guarantee the buses and trains will still be running on time! I knew I'd been here too long when I caught myself tutting that the bus was running 3 minutes late 
Hope the interview goes well tomorrow!