help fine tune a simple website, tidy up embedded gallery2

I have a very simple web site, that I changed all the pages to php and have a menalto gallery2 embedded in. I am "almost" to where I want it but the site sometimes renders strangely and I just need it tweaked a little bit. All my html pages were static but I moved to a common header and footer php which is being called from the other pages so I can make changes easily to those elements. Where I am hitting a snap is with the CSS syntax. The gallery CSS pages on my photo page seems to be overriding my other css file. I'm thinking it would be best to have the CSS for my header navigation bar and the footer be directly in those files, as opposed to the main css file. Anyway, my goal is a site that I can easily build upon and change content easily but I don't want to go overboard with something like joomla ( yet ) but if I like your work, and you can make a compelling case to go that route, I'd consider that later. I also have a "contact us" form script that I really like the functionality of, but after submitting a gap then appears below my header and the "thank you for e-mailing us" text. I don't think these ehnancements to exceed an hour for someone who is skilled with HTML, PHP, CSS and menalto's gallery2 CMS.