I don't know if this will help you Mikey, however...

When you compile a new skin (I usually create a ZIP with an HTML, CSS, XML and all my images) and upload it through the Host -> Skins dialog, it creates a new folder in \%SiteRoot%\Portals\_default\Skins\ with the folder name being the same that your ZIP was named, inside here you'll find all your files along with the ASCX file that it creates from the HTML. I would personally suggest designing in HTML until you are comfortable enough with the system to start creating your own ASCX files, there's not much difference except in HTML you simply place the [TOKENS] wheras in the ASCX you place the actual controls with their extended variables (any corrections are welcome).

It is in this folder I do a lot of my CSS tweaking since I can see the results real-time w/o uploading many incremental skins.

I would also suggest you grab a couple crash-course books in HTML and CSS, as it sounds like you're going to be dealing with this a good bit and a base knowledge of these will help you achieve the results you want.

Good Luck!

PS - As I said, I don't claim to be a guru, so if anyone sees any flaws in my descriptions, please feel free to correct me.