diff style on latest post, diff layout for single

Hi all,
I’m new to wordpress, but working my way steadily through a redesign from moveable type. I love all the functionality, and I’m quickly picking up the php ins and outs as I go along.
I have the feeling these two questions are easy to answer, but I haven’t yet seen documentation, on wiki or boards.
1) On my main homepage, I want to emphasize the latest post, probably by using different style tags in my wp-layout css. Can I single out the first post (latest post shown) and style it differently than the others shown on the page?
2) I want to put different lists on the side menu on single post pages (individual archives in mt speak), but it seems like single post pages are just the index.php layout with only one post inside “#content”. Can I change my side menu based on how many posts are being shown in the main content area?
Can anybody point me in the right direction on either one of these? Thanks much