Update Wordpress Site

I'm looking for some help regarding my current WP based website. I recently ported from wp.com to a wp.org site hosted by siteground. I'm a reasonably proficient user of WP so have managed to do the crux of the conversion myself (using the twentyten theme), but tidying it up and making it look a little more polished is proving a little beyond my ability. Here's what I'd like to do:

* Fix bug on blog roll where the featured image sometimes replaces site header.

* Fix the look of the featured image on the main blogroll page. At the moment the image is square and a little misaligned.

* Make main nav bar look a little less clunky and blocky.

* Resize right hand column on all pages to comfortably allow a 200x260 adsense unit

* Anything else you think you might be able to quickly tweak to make the site look a little more up to date/visually appealing.

There will also be the opportunity for more regular ad-hoc work going forward should this go well.