Although I haven't done it for a C30, I've lifted a few engines out and here are my thoughts:
1. make up a stand of some sort out of 2x6 or whatever, with casters on it. Pull the engine and drop it on the stand. (make sure the stand will go through the companionway!)
2. You can use a comealong, but they're a real pain to LOWER things with. You might consider buying a chain hoist - needs to be able to lift at LEAST 500 lb.
3. Although I've never done it, I don't see any reason not to use the boom. Although as Garbone says, use the halyard to carry the weight. Depending on your system, you MAY even be able to use your mainsheet to pick up the engine.
4. Pulling the engine itself is usually pretty easy (although getting the lag bolts out of the engine mounts can be a pain). The hardest part is usually getting the prop coupling off.
5. Don't forget to replace the engine mounts while you're at it! And check the stringers for rot and repair/replace as necessary.
druid