Is there anyway to refurbish the unit due to ageing without buying a new one. Also the bumper silver trim is scratch what can be used to polish it. Thanks in advance

 

Depending on your year of the car your better off just living with these very minuscule problems. Just clean and touch up the MMI with a detailer without letting any liquid get onto the MMI. As for the bumper I'd leave it be unless you want to get nitty and gritty.