Samsung UE46D5700 - OnScreen display Sleep Timer

[mmmmmm]

Hi,

assuming that I want to extend the functionality of my Samsung UE46D5700 with the following feature:
- once I set up a sleep timer, i want to have the remaining minutes displayed on screen permanently.

Can some one please provide a quick start in order to achieve this. Things like:
- how to set up a tool-chain for compiling the firmware
- where to get the libraries, source code and so on
- what compiler to use

Can this be achieved in another way: like adding extensions to the existing firmware?

Thank you