|If a diode actually burns there is usually some other cause, such as a capacitor or chip short. Maybe your mounting post was the answer.|
If that is the only problem then I suppose you have a fighting chance of replacing it if you are OK at soldering.
Obviously you need to try and find the full number - Google might narrow your guesses. As I'm sure you know it has to be the right way round. Maybe a meter will give some clue if you dare switch the mobo on.
You'd have to know a lot of detail about the board to say whether any other component has suffered. Maybe, maybe not, but burn outs mean a large current has flowed somewhere.
Mostly component changes on boards don't work out and I'm not hopeful. I suppose you've not much to lose as the mobo is defunct anyway. I should think any other damage, if any, has already been done.