I know this question has been asked quite a few times, but just looking a quick response as I don't see anything definitive when searching the forum.

On a 2.8 30v with 150k miles, will seafoaming the fuel system, crankcase and intake cause more harm than good? For example, will it clog up oil supply components, reveal otherwise non-problematic oil leaks, damage the o2 sensors, etc.?

 

I would only do it through the fuel system and intake, too much risk putting it in the crankcase with that mileage and the tendency of these motors to leak.