Cracked Cam Cover

First I want to thank folks (Benzmac, LarryBible, JCE, Ashman, others) for their help and informative posts. As an example, I was thinking about changing the timing chain on my M103 with 150k miles, but the explanation of the tensioners role in chain life has saved me $400 (or the headache of doing it myself and screwing up the timing).

Question: The other day I noticed my camshaft cover was cracked. I think "camshaft cover" is the correct term, meaning the whole black plastic cover the constitutes the top of the engine (not including the air cleaner of course). It seems the cover is actually made up of more than one piece (???) because the part that is cracked is isolated (separated by a long seam) to the portion of the cover into which each spark plug wire disappears into after coming off each plug. The crack (separation is probably a better term) seems to originate from underneath the distributor cap (??) (big black cap at front of engine). The effect is that the part of the cover that covers these wires is elevated about 7-8 mm beginning under the distributor cap, and that breakaway elevation decends to 0 mm about 25% of the way towards the rear of the cover. The primary width portion of the cam cover (the part with the oil filler cap) is fine. My questions are whether this crack poses any immediate threat to the engine and what it would take to replace the cap (just the cap, any gaskets as well, is the spark plug wire cover area truly a separate plastic piece from the broader portion of the cover).

Thanks.