I have no idea what that last part means. But I will read it today and see how hard it will be
Unless you try to wing it and improvise entirely (which I wouldn't recommend especially on your first try), you will need an adventure with pre-made maps, NPCs, plot points etc.
Off the top of my head FASA Star Trek had a very beginner-friendly one inside the main rule-book if you can track it down. Stupid yes, genre-deaf yes, but definitively easy to grok and prep for someone who does it for the first time.
Some people on the internets have also said good things about the beginner module in the old Japanese Enterprise RPG ( http://www.robertsaintjohn.com/groknard/JRPGEN_Enterprise.pdf ), although I have never taken a closer look myself.
The one you have me does have plot generator which I could expand on should help but I will look at that as well
I think WNMHGB is very beginner-friendly, as are all Microlite20 games. The only thing I'd skip are the ship combat rules, which are the most complicated part.
The biggest problem for beginners with WNMHGB is the lack of modules, so you'd either need to prep your own adventure or adapt adventures for other Trek/SciFi games.