I have changes that I'd like to make to the styling/CSS of our site. Can I do that myself?

The PICnet team would have to make changes to CSS for you.

If they are light changes and you know exactly what the are, our Support staff may be able to help you out. 

If the changes are going to be more extensive, and/or you need some guidance as to what needs to be changed you will likely be refereed you to our professional services team for assistance.

Open a ticket at http://support.picnet.net and list what changes you will need made, and we can help determine which way we would need to go with it.