Also, depending on your level of experience and/or knowledge of telephony, and in particular the Avaya Legend/Magix systems, my suggestion is to download the Legend Network Reference document in addition to any others you don't have, and read them. You will find most of the information you need in them.
Avaya's website: support.avaya.com
Then, post all the questions you want to the forum. This forum has a wide range of folks participating to help you.
Many times your answer can even be found by searching previous posts, especially on popular subjects, like networking switches, Primary ISDN, DS1, DID service, etc.
Happy reading!
....JIM....