Hello Christian24.
Before Ask how to remove a body, you first need to Ask how the bodies actually get added to the physics system. The Phys System currently maintains a list of bodies, each body is added when you call the EnableBody function, so its prepared for the next "integrate" call. By calling DisableBody(), its automatically gets removed from the list.
About the "destructable Objet", I probably will do just what Anonymous (76.170.117.x) said, perhaps adding Skinned Animation to the explosion. You can always try to make a rigid body dynamic by using joints, but an explosion probably will be too costy for the CPU.