Good Work! I would want to try to start it now, unless the fuel is really pouring out of the leak. Make sure the GPs are working. See below.
How can it leak from there, you asked? I can think of: 1. Loose pipe fitting; 2. Loose cover; 3. Bad o-ring seal. I did have one leak near there when the engine fell over onto the concrete floor before installing. That did crack the case. Of course, make sure it's reallly leaking from there. Since that is a low point, fuel could be leaking from higher up, or in front or behind, and end up dripping from the low point.
Glow Plug Section
D24 really needs ALL 6 GPs functioning for good starting. Depending on ambient temperature and general engine condition, ONE bad GP can cause a no-start condition. TWO bad GPs can cause no-start even in mild ambient temps.
Quick'n'dirty GP testing:
Visually inspect GP wiring and connections, especially the large diameter wires from battery + terminal to GP relay, and from GP relay to GPs, and GP bussbars. Clean corrosion if present. Disconnect battery first.
Measure voltage at the GPs when the system should be energized. Have a helper turn the key to the on position when the engine is cold, while you measure voltage at the GPs is near 12VDC.
Measure continuity of each GP individually. Remove bussbars and measure continuity between GP screw terminal and hex flats. DVOM should read 0 ohms or close to it. 1 ohm indicates faulty GP. You can definitively better test the GPs by removing them, and energizing them directly off the battery. Use thick wires (I use jumper cables) and watch for the GP tip to glow orange/red within 6 seconds.
More on testing GPs
here.