The period goes inside the quotations marks!
It only goes inside if it is a complete statement. For example: “she said it hurts “like the dickens”. The period goes outside. I am also a fan of the Oxford comma too lol
Nope, still goes inside it. Although what you're saying is true of questions and exclamations. For example:
"To be or not to be?" -- the question mark goes in the quotes because it's a quoted question.
But if you used this sentence: Did you use the phrase "hurts like the dickens"? -- the question mark goes outside because the question is not part of the quote. Same is true of exclamations.
Periods and commas always go inside (unless you're using a citation style that puts the period after the citation). For example, "Quoted material" (Citation).
For the record, I'm a fan of the Oxford comma when it clarifies. It is unnecessary, however, in certain examples (e.g., red, white and blue). Technically the comma isn't needed there because you have the word "and" joining the words white and blue. It's extraneous to include the comma, although, it's technically correct. Even the AP, which eschews the Oxford (or serial comma) in a simple series, says to use it when doing so would provide clarity.