Hi,
For the layout question, yes you'll need to create the CSS for that yourself. You can store your custom CSS in any file you like inside of your skin. I typically use the styleformwizard.css file.
I am not sure that you can change the text of the submit button without changing the resource file for it. I don't usually recommend changing the resource files because the can be overwritten when you upgrade.
There is not a way to conditionally enable fields depending on answers to other fields.
HTH,
Joe D