DigitalHumanitiesScholar, let me make sure I understand the situation. You have a transcription of a source document in plain text and you want to add just enough markup to identify section headings, people, places, and footnotes. Is that right?
An XML schema only allows certain elements to nest within certain others, and the TEI schemas that come with <oXygen/> XML Editor similarly allow only certain elements in certain places. So you can't take a plain text document and add only <head>, <person>, <place>, and <note>. Now, perhaps you are already planning to have <TEI> containing a <teiHeader> and a <text>, and the <text> will contain a <body>, and then you wanted to put your whole transcription inside <body>. While such a document would validate according to the schemas in <oXygen/> XML Editor, as soon as you begin adding <head>s, you will need to break the document into <div> or <div1> elements, each of which starts with a <head>.
For a personal or place name mentioned in passing in the text, you should use <name type="person"> or <persName> and <name type="place"> or <placeName>. The <person> and <place> elements are meant only for providing biographical and prosopographical data that occurs in certain types of documents, or which is added when creating a scholarly edition in TEI. See chapter 13 of the TEI Guidelines.
As for encoding footnotes, see section 3.8.1, which discusses whether to insert the <note> at the point of attachment (as in the examples in this section) or whether to use <ptr> or <ref> at that location instead. For an example that uses <ref>, see the cross-reference to section 3.6, which gives this example:
annotated text <ref target="#a51" type="noteAnchor">⁵¹</ref>
<!-- ... -->
<note xml:id="a51" type="footnote">text of annotation</note>
