Hi! I would say that the mechanical operation of the game is surprisingly smooth for most groups and most GMs - this is something I credit to one of the inspirations, Bluebeard's Bride, which made me aware how much a tabletop party often operates as a sort of single organism. All playing the same detective tends to go smoothly.
The place that people seem to find difficult is in constructing a Case and in generating new rolls as they go, which (I hope) the Case of the Signal Fire can help with by giving you a bunch of pre-written investigations, actions, and of course mystery scenario. There's also the advice section in the rulebook, which contains the principles I've used when constructing Cases, but I understand that putting together a mystery can really be a challenge. But, I have gotten feedback that Signal Fire is relatively easy to run - it's not an extremely tight mystery, but I've found players really enjoy the location, setting, and clues involved, including with World players (GMs) who haven't run very many games before.
So, using Signal Fire, it should be relatively easy; more challenging would be making your own Case. I would consider the actual mechanical operation of the game pretty beginner-friendly, though I would recommend a character-creation session for assembling the Detective (and, if your group's relatively new as well and uncertain, you might use the pre-written Player Component suggestions for Signal Fire, though tbh I think most groups pretty quickly come up with their own facets of their own Detective with those as vague guidance).
Let me know if you have any other questions or concerns!