Or more accurately, I haven't yet found the answer to.

Last week in our campaign I had two questions pop up: How are NPC stats added for groups? How do PCs aid each other?

I'm pretty sure the first one, if I recall correctly, is done by adding green dice to the pool for every NPC who is, for instance, targeting the PC. Like, if there are eight gunners and they're all firing at once at the PC, and the gunner's normal gunnery skill is 2Y1G, then he'll get an additional three yellow and one green die to his roll. But does this transfer to all rolls or is it just for a single "alpha-strike"?

Now as to the second one, what about when two PCs want to combine their skills in Mechanics to hack into a computer? I have no clue how to handle this, and I can't find anything in Skills or Talents that covers it in the core rulebook. I might have accidentally missed it, though.

Two PCs would combine their Computer skill to slice into a computer. You use the best skill level with the best characteristic level, if they both have skill in the attempted check. If they don't both have skill, the unskilled PC simply adds a boost die to the skilled one's dice pool.

Minions basically get a skill upgrade for every one of them after the first one as long as the Skill in question is on their skill list.

P. 25 EoE for un/skilled assists.

P. 390 EoE for minion rules.

But remember, that only minions act in groups, in the way 2P51 described; and they are always treated as unskilled, when there's only one. So they can never begin with 2Y1G and then start upgrading from there, as in your example.

Remember that any time you're dealing with NPCs, the first step is always to determine whether they are a minion, rival, or nemesis. The rules are very different for each and they should really be used for specific purposes.

A single minion in a group has no skilll ranks (even for listed skills), but every additional minion beyond the first grants one rank to the listed skills.

So, a group of four minions will have Rank 3 in all listed skill, six minions would have Rank 5... etc.

The dice pool works the same way as it does for PCs; using the skill rank and linked characteristic.

Assisting another PC in combat is done with a maneuver, requires that you be engaged with the ally in question, and imparts a Boost die.

Skilled/unskilled assistance works the way 2P51 explained, when outside of structured play.