Need some css pointers on a Twenty Eleven customisation

I have just redesigned the artwork on a client’s website and wrapped it around x-cart’s shopping cart software and now I’m doing the Twenty Eleven theme (it’s my first go with this theme) and I’m having a little trouble finding the correct bits of css code in the style.css file.

Hoping someone who’s more familiar with the theme than I am can point me in the right direction.

1) there’s a 28px gap at the top of the page in Firefox
2) the footer should be in the center
3) I would like the RH column to be all the way over the right. I found #secondary and changed the margin-right: 0; but this hasn’t moved it.
4) I would like the main column with the posts to be all the way over to the left and to fill up the rest of the 1000px content area.

I haven’t done one of these for a very long time and with Twenty Eleven, I seem ot be a little out of my depth.

(Note: there were others, but I edited the post and removed them as I fixed them)