Customizing date and comment pages

Hi all,

I am using theme ‘desire’ By Nischal Maniar, Version 1.2
One problem I find is that the dates and ‘Leave a comment’ widget appears with each published page which I want to avoid. Is it possible to hide the Dates and the ‘Leave a comment’ widgets on a published page?

Another issue I would also like to ask: if I update my site to the WP version 3.5.1, shall I lose some data? Is it possible that I update, but my site looks exactly the same like before?

Best,

B.