I want to activate the trip computer in my car been to local vauxhall dealer with a MFD screen for it to keep coming up as safe guy said its still paired to old head unit and can't un pair it. Got screen from scrap yard so have no codes for it

Now I have got 2 options:
1) Can anyone help me and un pair the screen for me so i can take it back to garage to get it paired to my car
2) Or I have been offered a paired screen and head unit would this simply plug into my car and work straight away. Only problem then comes as again I won't have the security codes for the head unit/display screen can these be obtained if car been scrapped? and when else would they be used?

Thanks for your help