Mapping SFDC field to Issue 'Entered by ID' using IF statement

I want to conditionally map the name listed in the SFDC Opportunity field to with that person's WF user Id in the Entered By ID field on an Issue. If the name doesn't map, I want to map my WF user ID to the field.

I'm using the formula below where SFDC_FieldName__c is the SFDC field, PERSON'S NAME is the contents of that field. The problem is that my name being mapped in all cases. What have I missed in the formula? 

if(SFDC_FieldName__c + "=PERSON'S NAME"; "60b78449000acce2307bf586e6a18d87"; "5a1301b900276ac1ca15e9aedb3b1bd1")