Hi Honeyann and Welcome to the forum
First of all I want you to know that you are not alone here. This is a wonderul place for information and unconditional support. I too was really frightened when I was first told I had this disease. At the time I had never heard of anything like this or what it actually meant for the long term. I googled and read everything I could get my hands on, unfortunately unlike some of the more common liver liseases there just really isn't a lot of infor out there. I found it helpful though to read things so I could gather questions for my doctor. I also found it helpful to write questions down as I had them so I could take them to appointments with me.
As to your questions regarding medications I started out orginally on Urso, which is a syntheytic bile salt I beleve, to aide in reducing my alkaline phosphate levels. This med which I still take has no real side effects and can be takin long term. I also was started on high doses of prednisone to reduce the inflamation and as a general immune suppressant. Generally prednisone is reduced to a mantance dosage (mine is 10mg a day currently), Prednisone has numerous side effects but can truly be a life saving med. It helped me tremendously with the extreme fatigue I was experiencing and gave me back part of my "normal" life. Aftter several months of being on my maintance dosage of pred, I was given Imuran which is a more specific immune suppressant. Initially I did not tolerate the imuran well and was taken off of it for several months. However as my enzymes became more stable and me and my hepatologist both were seeing more of the side effects of the pred, he decided we should try the imuran again. This time I have had no trouble tolerating it and my enzymes have remained stable and nearly in the normal range. I also take lasix and aldactone for fluid retention. Honestly when I look at some of the other people here and all the medictions that they have to take for there liver problems, I feel fortunate. The only inconvience so far is that with the imuan you must have monthly blood work as it has a tendency to deplete some of minerals (potassium I know is one) that your body needs.
There are seveal people on this forum that have AIH and have successfully lived with the disease for many years. As scary as this all seems right now, there is hope that it is managable if not curable. Educate yourself so that you can communicate with your doctors. If you do not have a hepatologist now you should talk to your doctor about referrring you to one that has experience with AIH. I hope this was helpful to you.
My thoughts and prayers are with you as you begin this journey.