All computer suppliers tend to purchase a laptop carcass, be they Apple, Lenovo, Dell, HP etc.
The carcass will include the case, motherboard, screen & keyboard. All the supplier will add is CPU, RAM, optical drive and hard drive.
There are so many things that can go expensively wrong when building a laptop I wouldn't even start but if you do try one thing I would advise is that you make absolutely, positively 100% sure that the display you buy fits the case and is compatible with the graphics chipset on the motherboard.
When I did PC repair we would have 4 or 5 makes of each size & resolution screen, because some screens just wouldn't work with some chipsets...
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