Would like to know if anywhere there is a website, video, tutorial or just a friendly person that could help me get my feet wet with a basic modding thing: speciafically, forcing the appearance of a particular custom livery under x, y defined conditions (like the IR coaches and BR 101 substitution mods for LFR).
Try the PC Editor subforum or the community-created documentation/tutorial document linked in this thread.
Unfortunately, what I want to do does not appear to be possible (at present) with the official editor. It's straight-up hack-modding.
I don't have a clue how stuff like that work either. Maybe you could get in touch with TaskPlays the respective mod creator of the BR 101 substitution and IR & SBB EC Coaches mod. If you do, maybe ask him if he can make a mod to get the expert 101 and the IC cab car for services into LFR, once its out.