contesting a major amendment to a revocable trust?

(Tempe az)

Don't know where to start, much less what needs to be done if anything can be done still to contest a major amendment made to the trust during a questionable period of time when my uncle was incapacitated?

My uncle passed away in nov 09'. He had both a will and a revoc trust made up in july of 08'. the original Revoc Trust named my grandmother his sister as the primary Beneficary of and was to be distributed the balance of family trust estate!

Over the last year of his life he spent at least 10 months in hospitals, long term care facilities, and a private respite home, before passing away in hospice. Just to name a few major health conditions my uncle suffered from he suffered at least 3 strokes, was diagnosed with terminal Lukemia, and had a bout with a serious case of influenzia and spent almost 2 weeks in the hospital trying to recover while also beginning to succumb to the pain and effects of his lukemia. He was on a feeding tube due to trouble he had trying to swallow, He could barely communicate verbally and could barely lift his arms up.

I visited shortly him on oct 14th on that day he could barley speak as for understanding him was almost impossible!

The following day however a major amendment was made by him which deleted completely from the trust and leaving the balance to be divided and distributed among his surviving nieces and nephews who listed as beneficiaries only in the case that my grandmother was no longer living at the time of his death.

Coincidentally on that day the successor trustee invoked his power and terminate my uncles trusteeship due his incapacitated physical and mental state!

In addition the successor trustee was not only my uncles Financial planner, but also his nephew and is also listed as one of 12 benificiaries listed in the family trust which he will benefit from substantial from the first and only amendment that was made deleting my grandmother from the trust entirely!

my family has no idea where to start or what to do. The entire estate is estimated between $500,000 - $750,000.

Also the copies of the trust established on 07/09/08 stated that a schedule/list of assets included in the trust, was suppose to be attached with the copies however after 2 request from benificaries listed still have not received mentioned schdule and no attempt has made to give explaination/answers to questions reguarding of the estimated value which was stated in the letter sent out with the copies of the will and Trust $250,000 the trust.

can anyone help me?