There are also translations around that come via the Chinese cannon instead.
The suttas are probably very hard to understand without background knowledge or commentary (or, really, actual practice), but of course I don't know which of the commentaries GP refers to. The dhammacakkappavattana sutta, being one of the important/famous ones, has truly voluminous commentary from truly voluminous sources.
GP refers to "continuous effort to face the uncomfortable". I'm not sure that I'd use that sentence to summarise the Buddhas teaching to be honest. But I suppose that it could be a reference to the 6th limb of the noble eightfold path (right-effort), or the 7th (right-mindfulness), or to the 1st noble truth (the truth of unsatisfactoriness/ suffering).