You should find a addiction specialist doctor or counsleor that can advise you on how to taper.. Benzo's like xanax and valium must be tapered very slowly.. no exceptions. It is very very dangerous to quit these cold turkey.. you can have seizures or possibly worse.
I don't have knowledge of liver damage from benzo's but I assume that its possible.. I would ask your doctor about milk thistle its a supplement that helps rebuild and detox the liver.. may help you get it better..
Are you sure it is the xanax that is causing the liver problems...then again, you may be having an adverse reaction. Withdrawl is possible but should be done slowly, preferrably at cutting by 0.25mg per week. I am so sorry that your liver enzymes are acting this way. Be sure to look into other reasons that your liver might be responding like this. God Bless, Steve
PS Although xanax is highly addictive, contrary to what most people think, there are many drugs and substances that are far worse!