Honestly, the #1 reason I felt ready to jump in was because I’ve listened to hundreds of hours of Friends at the Table. Although they only play Scum and Villainy for the second half of Twilight Mirage, the majority of the games that they play share the same general improvisational ethos and it’s really helpful to hear Austin’s approach to so many different situations. I’m also a subscriber to their Patreon (https://www.patreon.com/friends_table) and at the $5/mo tier there’s a monthly tips cast that’s full of super useful information for running these kinds of games.
It requires a different approach, but once you embrace it I think it’s actually easier on the GM than D&D. I don’t know what your D&D experience was like, but for me I wasted so much time prepping possible things that the players could do, people they could talk to, etc only for them to entirely miss all that stuff. I also always stressed about keeping them on track for the thing I had prepped because if they went off it I wouldn’t be ready.
Because Scum and Villainy (and all the Forged in the Dark & Powered by the Apocalypse games) is much more collaborative and encourages players to invent things out of the blue, it forces you to let go of prepping everything which at first I was really nervous about but I actually found to be really freeing. This is not a game where you as the GM create the scenario and are a facilitator of the players experiencing it - they are co-creators. If they come up with a cool idea, ask them to flesh it out. If their action fails, ask them if they have any ideas for an interesting reason it could have gone wrong.
The book explains this but it didn’t really click until I had played just how much the system propels the game forward. The mission always starts with the players in a position that demands some kind of immediate action. Regardless of how well or poorly it goes, the specific action they choose and the result of their roll will point to a pretty specific outcome, which gives them another situation that demands action. It’s a really tight loop that doesn’t leave a lot of space for “what do we do now” both from their side and from your side.
One other thing: my players chose the Cerberus ship (bounty hunters) and for me, the absolute most useful prep I did was binge-watch Cowboy Bebop in the few days before we played. The game is designed to around the loop of an episodic TV show - get the mission, plan the mission, run the mission, get paid. Being steeped in the genre is, IMO, the most useful thing you can do to help yourself be ready. When the player inevitably does something you didn’t expect or plan for, you’ll have a catalogue of little snippets of cool shots and scenes to pull from when deciding what happens.
That was kind of longwinded and rambly but I hope it helps. I’m hardly an expert having only run one game so far but if you have any questions or want to chat about it feel free to DM me. Also - I’ll send you the action report I wrote up of our first session so you can see how the game flowed and the rolls played out, to give you an idea of what it looks like in practice. Hope that helps!