How do i change a/c from celsius to fahrenheit on 1989 cadillac deville? same with gas, litres to gallons?

just bought a 1989 cadillac deville fleetwood d'elegance.



the (electronic) a/c reads in celsius and the gas meter reads in liters. how i change both from celsius and liters to fahrenheit and gallons? this would save me from buying a $29 cadillac manual.



thank you for anybody who does help, smartass remarks like %26quot;buy da manual LOLZ%26quot; need not apply.How do i change a/c from celsius to fahrenheit on 1989 cadillac deville? same with gas, litres to gallons?
Best to ask a mechanic in his spare time to save cash,.