Not very important. Having big biceps won't get you up the mountain any faster. have strong legs and good cardio are infinately more important. That being said, having a strong upper body won't hurt you either. It always feels good to get atotal body workout. If you have limited time to work out spend as much time as you can working out your legs and treat the upper body as "extra".

Also, to add some advice about calls: The hoochie mama is nice because it's very easy to get a decentsound out of. However, it would be worth your while to learn to use diaphram calls. Not only can you vary your sound more when you get the hang of it, but you will be glad if you find yourself at full draw on a moving bull and need to call to stop him. This is something you can't do with the hoochie mama in your pocket.

And to add what has been said about boots: good socks can also help to avoid blisters. synthetic/wool socks work well and dry fast. get a few pairs of midweight hiking socksby Smartwool, Thorlo, Bridgedale or Danner. They can be more expensive but your feet will be better off for it.