D7000 right for me?

Hey guys, I am having a rather hard time picking out a camera. I first bought a Canon EOS T3i and liked it but didn't like the limited autofocus and the cheapness of canon's consumer lenses.

Then I bought a canon 50D which was better and felt good in my hands but still I sold it later because the image quality was not that terrific.

I bought a Sony NEX 7 which is great but I am getting rid of it because I would like to have a camera with weather sealing.

I hear that the D7000 has weather sealing, plus takes two cards at once so can be used for critical work. I am intending to take a camera on a long backpacking trip.

What are the important differences between the D7000 and the D300s?

Does nikon make weather sealed lenses that are not exorbitantly expensive and can be used for landscape work. Something like the canon 24-105 would be ideal.