Place block at X, Y and X

[xoft]

Protection should work by disabling the breaking altogether, rather than fixing the aftermath. If the offender breaks a chest, you'd have to replace all the contents - it'd be much easier not to break the chest at all. See the OnPlayerBreakingBlock hook for details on how to do that:
http://mc-server.org/wiki/doku.php?id=ap...akingblock

As to your question, block placement is done using cWorld:SetBlock() or cWorld:FastSetBlock(); the difference is that FastSetBlock() doesn't trigger block updates and doesn't process block entities.