Replacement main board for DL4100

Hello,
Just like many other users, My DL4100 stopped working with same symptoms of flashing blue LEDs, blank display and restarting by itself every few minutes. It has 4 x 6TB in RAID 5 configuration.

1- Is there a way to manually re-flash the boot memory or upload the latest WD image?
2- Is there a replacement board for the DL4100?
3- What is the use / purpose of the 4-pin connector in the main board located near the cooling fan connector?