Ok looks like I managed to learn all I needed by myself.
I found this pretty good app online.
index
And for people who don't know (like me),
"You can buy one ticket for the whole journey, although it simply additions the three companies' fares, without discount. E.g. travelling for one station on the Toei Aakusa line, then one station on the Keikyu line is convenient because there is no change of train, but you have to pay the fare of two separate tickets."
source :
Tokyo Guide : Transportation in Tokyo- Wa-pedia
Phew, I'm happy to have planned this at home instead of in the middle of a train station.