1) There are some threads around for this, I might do a search later on if I have more time, but you'll probably find them yourself faster.

2) Wherever there are Greeks struggling under tyranny, my friend! As the KH you'll have lots of Greeks poleis revolting to you. Trying to reinforce all of these revolts makes a very interesting campaign.

3) I think there were some reforms tied to the vanilla marians, so you have to wait till the Romans have a second huge city (probably Capua). I don't think there a some reforms you can trigger yourself.