Yes, they tried to/did tamper with the ball. Basically the idea of ball tampering (if you are that way inclined) is to rough up one side of the ball, whilst leaving the other side smooth, so the air passes differently over the two sides and makes the ball swing more.
If you are a skilled bowler, you can bowl it onto the same spot every time, thus achieving a natural scuff and smooth side. But alas these boys didn't have the skill/time to waste on that!
And then the second part (without names, as I was terribly bored by then). A senior player told the junior bowler to do it, apparently they have sandpaper in their kit for smoothing the bat. Captain saw they were chatting and suspected what they were up to, but instead of stepping in and acting said to them "I don't want to know what you're cooking up there". Coach said he had no idea this went on.
Young bloke gets caught (banned for 9 months), senior player confesses/caught out (banned 12 months, can never have a leadership role), captain reprimanded (not playing for 12 months, no leadership for 2yr) for not taking a leadership role when he could see they were up to no good. Coach tried to keep out of it, but has also resigned.