How do I reach the Dymo LabelWriter 400 printhead?

Is there a tutorial to open the Dymo LabelWriter 400 and reach the printhead to possibly clean it directly?

Print is fading and using the usual methods to clean the printhead (i.e. cleaning sheets or running a business card through the label feeder) doesn't help.

I was wondering if the printhead is now gone (the machine is pretty old, though it has been mostly used in the last 3-4 years) or if it can be cleaned directly on its surface to recover functionality.

I can't find info on opening/tearing down to reach the printhead (I see it but I'm not sure what to do now)

thanks in advance!