Hello to everybody.
Few days ago someone crashed on my '87 k100 while it was parked and left. When i found it out i saw that the cover has a crack (because its been hit direct at the corner it is very small) on the front lower side and there is a small oil leak ! I m thinking of opening it and try to weld it. 
     My questions are :
1) should i empty the engine from the oil or its not going up there while the motor is not running
2) Can it be weld or must i start searching for a new cover
3) If there is green light for the above ... must i change also the rubber between the block and the cover ?
     Any help is appreciated

Some oil may come out but only a very small amount. You should be able to weld it and as for the rubber gasket, yes I would replace it as well as the rubber rings under the bolts that hold it on. New rubber rings will help the gasket to seal properly.