As far as "hunting through stylesheets" you absolutely do not have to do that if you use an appropriate helper tool (what I referred to as a "CSS sniffer" earlier in this thread and also posted a link to a review of).  Such tools tell you exactly what CSS is currently being applied (so you can see if the issue stems from PADDING or MARGIN or whatever).  The tools can also tell you which source file(s) each CSS attribute is defined in so there's no file system spelunking needed to track down errant style definitions.  The tool I linked also shows you a simple graphic representation of the positioning-related CSS attributes for a selected page element.
 
If you absolutely hate the idea of installing an inspection tool (browser addon) then perhaps you'll be willing to try out the Google Chrome browser's "Inspect Element" option on your logo.  Load your page in Chrome, right-click on the logo, select "Inspect Element" and then expand the "Metrics" panel in the right column of the "Inspector" pop-up box.  The "Metrics" area shows a graphical representation of the selected page element's applied MARGIN, BORDER and PADDING values (if any) as well as the rendered size of the selected element.
 
Above the "Metrics" panel is the "Styles" panel.  This shows you all computed and inherited styles as well as the source files for applied CSS.  Again -- no file system spelunking needed to track down CSS.  You just need the right tool (and it's free).
 
Good luck-
-mamlin