As long as everything is operating, 91.213 (including MEL's) does not apply, so no, you don't need one.
If you're flying Part 91, it's a fairly simple procedure to get an MEL authorization.
You simply write a letter to your FSDO, requesting authorization to operate your type, N-number, and serial number under the MMEL (yes, you use the MMEL under Part 91...more later).
There are "M" and "O" procedures required for certain items, and you have to develop those yourself. Unlike Part 135/121 operators, you do not have to submit these for approval. You simply make them up and use them.
If you haven't operated under a Part 91 MEL before, you will probably have to have a meeting with FAA inspectors as to the proper operation under the MMEL.
The end result is that you will get a Letter of Authorization that allows you to use the current MMEL and your "M" and "O" procedures as an MEL.
AC 91-67 outlines the procedure.
Fly safe!
David