You can add a custom style, see the settings or you use the markup and inline style; like
<span style="font-family:"Times New Roman",Georgia,Serif;">text</span>
THe plugin use the language files, if you set the install to your language, then use the backend automaticly the language files. The plugin is also usable in ru_RU; but the file is old and not include all strings. Maybe you can create a new file? The frontend use the strings inside the settings and you must change to your language, write the new message.
Hier you all current language files: