How can I change the font size, style an so on? Is it easier to code it in or is there a plug in that makes everything simple?
Check your template css file. Appearance/Editor (Edit Themes). Best to edit the file itself using notepad and uploading it using an FTP software. And make a back up with the file.
As mentioned above WordPress is based on a Templating system that uses CSS files. CSS controls the font attributes. Each template is different. You need to find the CSS files for the part of the template you want to modify and change them. If you know little about CSS and templates you'll likely do more damage than good.
Are we talking about the text in Post content, in the theme, or elsewhere? Are we talking about a wordpress blog hosted with a hosting service like wordpress.com or the regular version that you download and host yourself? Please remember specifics and details are always a plus when asking for help.