The easiest method would be to use this script:
// Replace fonts in current INDD doc according to a set list
// Each line in theFontReplacements: 'Existing Font', 'Existing Style', 'New Font', 'New Style',
// Styles are optional - leave blank ('') if unwanted
var mydoc = app.activeDocument;
var theFontReplacements = [
'Minion Pro','Regular','Calibri','Regular',
'Trade Gothic LT Std','Regular','Calibri','Regular',
'Trade Gothic LT Std','Bold No. 2','Calibri','Bold',
'Trade Gothic LT Std','Oblique','Calibri','Italic',
];
for (i = 0; i < (theFontReplacements.length/4); i++) {
app.findTextPreferences = NothingEnum.nothing;
app.changeTextPreferences = NothingEnum.nothing;
app.findTextPreferences.appliedFont = theFontReplacements[i*4];
if (theFontReplacements[(i*4)+1] != ''){
app.findTextPreferences.fontStyle = theFontReplacements[(i*4)+1];
};
app.changeTextPreferences.appliedFont = theFontReplacements[(i*4)+2];
if (theFontReplacements[(i*4)+3] != ''){
app.changeTextPreferences.fontStyle = theFontReplacements[(i*4)+3];
};
mydoc.changeText();
};
The only downside is that you have to manually specify the font changes. The upside, however, is that you can specify premade conversions to be used again on recurring jobs or projects!
Installation is simple, copy the script into a Notepad editor and save it as a .jsx. Then you open the scripts panel and opposite click on User and click Reveal in Explorer.

Copy and paste your new .jsx file into the folder and you are all set!