Rupert

Hi, I have a 2009 Golf V 2.0 TDI and need to change the starter motor. How do I prevent losing all the codes when I have to disconnect the battery? I don't have a plug-in diagnostic reader to reset anything and wouldn't know how to use one. If I lose the codes how do I find out what they were or is there a default setting? As you can tell I don't have any knowledge about codes as my mechanical skills are centred around vehicles from the 60s to the 80s. Thanks in advance for any advice. Rupert