I'm not sure what you mean by "photoshop cs3 output to css", maybe some new feature in cs3 perhaps?
Anyway its a really bad idea to rely on such tools, especially if its made in photoshop. Generally WYSIWYG tools dosn't have a place in professional webdesign, they are only good when someone need to publish a document in a hurry.
Most webdesigners who care enough about their code are using text editors such as notepad, and at most coding tools with features such as syntax highlighting and/or autocompletion.
Photoshop is however a very nice tool to create graphics such as, buttons; borders; backgrounds; and logos. Its Grouping feature is very useful when having lots of supporting graphics or different layouts.
It may also be worth to mention, that choice of tool usually depends intirely of the project size. If you got a few hundreds lines of code, it may be more convenient to chose a editor which allows to hide chunks of code such as, functions, if statements, or even individual selectors in a stylesheet. I mostly prefer just to use the lightweight tools such as notepad, however syntax highlighting dose speed up my work in bigger projects.
Its not hard to work with CSS at all, it used to be because of browser specific problems, but IE7 pretty much was the end of that. So unless you want to support lots of broken/outdated browsers, it won't be hard. Just keep in mind that most css properties are easy-to-understand plain english, even the values are pretty much self-explanatory.
The below will thech you most of what you need to know, to work with css, i do also suggest you learn about CSS Selectors, since that will make it easier to style your documents in a clean way.
http://www.brugbart.com/Tutorials/17/ - HTML 4.01
http://www.brugbart.com/References/6/ - An Introduction to CSS
http://www.brugbart.com/References/117/ - CSS Selectors
Finally you should not neglect to validate your code, having valid code will solve a huge range of problems.
http://validator.w3.org/ - W3C HTML Validation Service
http://jigsaw.w3.org/css-validator/ - The W3C CSS Validation Service