Chanchamayo seems to be easier destination to visit without knowing Spanish and doesn't require as much advance research as Tingo Maria. Based on my experience, Transportes Junin seem to be quite OK bus company to La Merced.

Anyway, I was a couple of years ago in Tingo Maria and most tourists in Tingo seem to be day trippers staying overnight in Huanuco. This might be outdated but I would research in advance whether there are companies in Tingo selling tours.