The easiest way to make an auto bed leveling system is to use an inductive sensor (for example LJ12A3-4-Z / BY) and an aluminum plate instead of glass on the printbed. This one mounts to the fan holder that comes with the printer.
You will need an M5 (25mm) bolt and a hex nut.

https://www.youtube.com/watch?v=EcGFLwj0pnA this great guide shows how to do it. I've added my configuration.h file for Marlin 1.0.2. to thing files since for my K8200 I had to make some different settings.