You can do it on chromie on/off or wm on/off, each will have it's own event cooldown. It's pretty hard to solo, you'd probably want a 50 with you. The second wave has a ton of mobs sitting by towers you need to kill to complete that wave so if you're not ranged it's rough.
No quest or anything, the event will just spawn the friendly npcs.
Just if you didn't know, all those gems have been nerfed in an upcoming ptr build, so unless you're happy with some gems for (most likely a couple days, I imagine the patch will be when the Shadowlands event will hit on Tuesday), I wouldn't worry too much about it.
Could be wrong and the ptr build might be for Shadowlands release.