Modifying the css (layout)

Hi, i downloaded the theme (it’s very good) and i’m changing some things to fit my site style.

Some thing i need to know, if you could help me:

– How i disable the fixed style on sidebar to normal scrolling?
– Is there a way to enable WP-Pagenavi for this theme?
– How i set the width pixels of the search form at the top (in firebug it show that it’s in a page, and i not found it)? And how i remove the expanding in the same search form when it gain the focus?
– Is there a way to upload a logo withou messing with direct CSS and image paths?

Sorry for the multiple questions.