Jo, first of all I really like your design. I think the color scheme is great and I was immediately impressed. Good job. The one thing I would like to see different is to have the entire page centered in my browser instead of being up against the left edge. But overall I like your design a lot.
The sheep look fine to me. Is the problem that it doesn't look good in print? You probably needed to use more PPI when you created it. I'm guessing you went with 72 PPI for the image online, but you generally want more information for printing. I usually use 300 PPI for anything I think will end up being printed. I don't think there's any good way to convert the image to the higher resolution.
I'm not a graphics expert and so I'm not sure if you can convert this easily to a vector image. Hopefully someone who knows more than I do will drop into this thread. The image does look like one that would scale well as a vector, but I'm not sure if you can convert the current one of if you'd need to create a new one. I suspect a new one will be needed, but I've certainly been wrong before.
As for the code, yeah, it could be improved. I do see a lot of empty <div> tags. Using css to layout a site is definitely a better approach to coding for a variety of reasons, but there are plenty of sites still using table based layouts. Don't feel like you need to rush to convert the site to all css.
Better would be to take the time to learn how to develop an all css layout and when you feel more comfortable you can rework the site.
DreamWeaver does have decent support for css, but I think it will only create a table based layout. It's been awhile and a few versions since I've used it so that may have changed. Personally I think the best way to develop is to hand code. Hand coding forces you to learn the code better and once you've got a handle on things development is just as fast as using a WYSIWYG. Most hand coders, myself included, would tell you it's quicker to code by hand once you know how.
You could use an editor as simple as Notepad, but there are better ones. I use
HTML KIt, which is a free editor with a lot of nice featues.
PS Pad is another free editor, which I've recommended to people and there are many more free editors.
For learning the code a good place to start is
W3Schools. Simple tutorials that pack a lot of information in them. I learned css through
Eric Meyer's books and I'd highly recommend any of them.
Ultimately the way to learn to code is by coding. Grab a book or find a tutorial online and start typing in the code they give you. Then play around with that code some and see if you can do some different things. When you're comfortable start developing some web pages from scratch. Hand code these even if you decide later to go back to DreamWeaver.
HTML is pretty easy to understand and use. Much of CSS is too. A full CSS layout can be a little tricky and will take some practice to get right and then with each new site you build it'll get a little easier and you'll discover better ways to do things.
It's worth the effort and time.