importing xml text and style sheets into wordpress format

Thanks to anyone who has a chance to help me figure this out. As you can see by my user name, I’m not much of a programmer so the simpler your response the better it is for me…

Question: I need a on-line public document that is available in xml and html formats put into a wordpress format. The style sheets are visible with the xml and html content that I need. Is it difficult (for someone who knows what they’re doing — read: not me — to make that conversion? If the files can be brought over, can the style sheets then be easily changed (e.g., “header1” was originally 10 point Calibri and I want it to be 12 point Verdana…)

Thanks again to anybody who can point me in the right direction!