Yes it's possible to replace just the screen, it is basically the same process as replacing the LCD on the 12" Retina. After removing the assembly from the MacBook, heat and slide a thin tool under the bottom glass, then you can remove the screws for the hinge and start removing the screen. Would definitely recommend against replacing this unless you have replaced the LCD only in older models, a lot can go wrong.
Not really worth it at the moment unfortunately, LCDs go for 300$ if you are even able to get hold of them, which is far too expensive for an LCD. Wait till later this year, and they should become more available and drop in price.