change the dispaly with a 2012 MacBook Pro

No - generally you can not change between model years… especially several years (some parts will swap a year older or younger but beyond that changes in design and specifications eliminate that possibility)

For example some of the '12 MBP screens are dual graphics (your old box's GPU could not support that) some have IPS technology (again something not on the '09 box). On some boxes' you can't even swap a Matt for a Glossy screen (or vise versa).

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