If you want to rename ABAP classes, methods or variables you have two possibilities: Feel the pain or use Eclipse...
It's pretty simple! Just right click on the object and choose "Rename":
But that's not all - every reference will be renamed! So this is a killer feature if you want to move objects in your namespace...
Unfortunately this doesn't work for function modules and function groups, there you need to use function module RS_FUNCTION_RENAME and update the references manually.
If you haven't downloaded ABAP on Eclipse yet:
https://eclipse.org/mars/
https://tools.hana.ondemand.com/
To see the full Features of refactoring in Eclipse, take a look at
http://help.sap.com/saphelp_banking450sp06/helpdata/en/4e/c859406e391014adc9fffe4e204223/content.htm... (thanks to
thomasfiedler)