Add Content Right Below Top Navigation

A couple of questions about the network theme please.

1.) How do I add a form or other html code to the space directly below the top navigation?
2.) How do I remove the "currently powering 1 blog" button on the upper right hand corner of home page?
3.) Where do I add Google analytic code to the site?
4.) How do I change the home page from a three colum lay out to a 2 column lay out?

THANKS for all of you help!