While taking the cylinder head off my 3.0 M103 engine i broke the very top half of the outer timing chain guide rail (the more straight one),,, can someone tell me how critical the top of this rail is for proper operation and also if it does in fact need to be replaced, what steps are involved, how much time am i looking at?? The head will be ready tomorrow and i wanted to just get it back and throw it on and go.... Also does anyone know if i should drive it under a certain speed for a certain amount of time after the head gasket is replaced to let it seat properly, or can i just drive it like normal??