The way I would do this is with a Derived Column Transformation. Take a look at this example (hitting the sample database, AdventureWorks2012):

As you can see on this screenshot, what I'm doing is taking the Name column from AdventureWorks2012.HumanResources.Department (this would work with your version of SQL Server/SSIS as well, I believe. Although you would know pretty quickly if it doesn't) and using a conditional statement for my Expression:
Name == "Sales" ? "New Sales Name" : Name
What that is, is a short-hand conditional statement. It takes the Boolean result of Name == "Sales". If that's true (i.e. the Name is "Sales") then return "New Sales Name", or whatever string you'd want to substitute. If that's false (the Name is not "Sales") then just return the Name as it originally was.