As you don't have a skill relating to d'en, I'm linking this to the skill related to de phrases and en.
I'm guessing that d'en, as I keep hearing it, replaces "des/de + noun" (though I'm still somewhat confused about it). But it is really necessary to use d'en? Couldn't you just use le/la/les (or in some cases, ça/cela). As in "J'aurais mieux fait d'en prendre." could I just say "J'aurais mieux fait les prendre"?? If d'en is required, how do I know when I need to use it as opposed to le/la/les (apart from 'fixed' expressions like "d'en haut")?