A change in design calls for a global change of a font. Presently there are no font problems present.
Say for example you have a book that uses three fonts: Times for the body copy, Helvetica for the headings, and Helvetica Narrow for callouts. You've decided to replace Times with New Century Schoolbook.
DefaultFamily=NewCenturySchlbk, Times, Times New Roman, Tms Rmn
You don't have to have anything after the New Century Schoolbook, but it doesn't hurt.
If you want to specify a substitution for several fonts, you can edit the other parts of the ini file. For more information, see this page. Also, additional information, as well as a large set of Mac-Windows INI entries, in Adobe Knowledgebase article the aging but still valid Adobe Knowledge Base article Common Font Aliases for FrameMaker 5.x for Windows..