E30 - Broken Rocker Arm

[Stavros Theodorakopoulos <stavros@xxxxxxx>]

I have an '89 325i, 240 k.  Yesterday without warning, the car starting
rumbling, and I lost a lot of power.  I just took off the head cover and
found the upper rocker arm (I think at the intake valve stem?) snapped
right off.
Has this ever happened to anyone?  Should I worry about others
cracking?  I'm probably going to have a shop do the work, but I'd like
to know if anyone has attempted this on their own.
Since the cylinder head will have to be removed, are there any upgrades
I can make to these components, (ie. camshaft, valves, rockers etc...)

Thanks in advance.

Stavros
stavros@domain.elided

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