The most likely cause of the lack of compression is a burnt or badly worn exhaust valve or seat. A cracked head would have to have a huge crack in it to leak any measurable amount of air. Take it to a shop that can do a leak-down test. This will do two things: first, the test will pinpoint exactly where the air is leaking, and second, usually if a shop has this equipment, they are likely a bit better at diagnosing engine problems and fixing them.
Now for the next part. After confirming that your engine needs head work, you'll need to find a good shop that will do your head the right way. These heads are fussy about the height of the valve tips after all the work has been done, and most shops will try to even the tips out by grinding them down. Wrong thing to do! Beware!
Before I freak you out too much, get the test done and post the results, and we'll take it from there. Parts, advice, and tech support are readily available from Primatech .
