How can I change the default replacement font in Find/Replace Font?

I'm going to disagree with @Derek Cross and @Joel Cherney to a small degree.

I see no harm in editing the [Basic Paragraph] style AS LONG AS IT IS NEVER USED FOR ANY PURPOSE. Whether there is any actual benefit to doing it under those conditions seems debatable. Changing the default font outside of styles as Joel suggested is an excellent choice.

I can't endorse Derek's post hard enough. I suspect what you're trying to do is to configure InDesign so that you have to engage in less repetitious clicking, right? You have a default font choice for all your work, and you don't want InDesign to keep on suggesting Minon, because it's not your preferred default font you're going to be using for the majority of your projects. 

The best way to avoid doing that repetitious work is not to try to configure InDesign's base font settings to your preferences. Instead, it's faster & safer to build on top of InDesign.  For example, if you foresee a frequent need to replace someone else's fonts with your own default font, a script like Peter Kahrel's font substitution script is a more reliable solution that is less likely to cause major challenges when working with someone else's files. If you'd like to read some descriptions from other seasoned InDesign users regarding why it's dangerous to modify the Basic Paragraph style, that won't be hard at all to find.

(Changing your default font in the Character panel with no documents open is an excellent way to customize your installation, and isn't relevant to problems caused by altering the default Basic Paragraph style, or to InDesign's hidden font defaults.)

It's not advisable to change the Basic Paragraph Style, instead create new parent style based on [New Paragraph Style].As Community Expert Scott Falkner has written:  Because any changes to Basic Paragraph Style will certainly mess up formatting when copying and pasting text between documents.