Tell you wife to google Kaffe Fasset, an amazing knitter, and he's a bloke.
I remember when I first started doing cables and fancy stuff. I was so worried about getting it right, and losing stitches along the way, it got SO darn tight I could barely get the needle through the stitch.
My mother about beat me round the head with it.
By the time you get to the end of the scarf it'll be great. In the meantime just take it steady. And if you get stuck, this is a great place to be, as is YouTube.