Ok_ let's see...
The header height is specified in style.css:
background: url("images/header.png") repeat scroll 0 0 #111111;
margin: 0 auto;
However, if you increase or decrease the header height, you'll also have to adjust the position of that top nav bar (again, a simple CSS amendment to the top padding for .headerright in style.css should fix it). Using Firefox & Firebug, I can increase the header height to 450px or above without any problem. Nor sure why you couldn't see any difference in the 250 - 450px range.
Incidentally, I strongly recommend using Firefox with the Firebug add-on for this kind of work as you can try out CSS changes on the current page without actually editing the site's stylesheet. Useful for tweaking things like heights and padding.
I change page 2 from About to Dedication and I notices it is still in the url above - can you tell me why
The page's slug (its permalink) was generated when you first gave the page a title ("About"). That slug (/about) persists even if you then change the title. You have to actually edit the permalink to change it. Edit the page and click on the Edit link just below the page title and to the right of the permalink. Then change the permalink to match the title.
Don't do this too often, though as it will break any back links that you might have on other sites.
dedicated to my dad and I want to make it as good as i can
I think that's a wonderful idea and you're off to a great start. If I could make one comment, it's that it would be nice to have a photo of your dad on the front page to go with the text.