I am interested in Islam Religion and recently I have had some
researches. While reading the history of last trip of ?Prophet
Mohammad? before his death, I understood that by finishing Tamattu Haj
ritual, in return he stopped at a placed named  ?Ghadir(-e) Khum? 
(between Mecca & Medina) and asked everyone to stay for some
days. He had some speeches and remarks over there which is the base
for Shia Philosophy. I want to know everything about it in details, if Sunny
Muslims accept this "last will" and why Shia celebrates this
anniversary? I need to find the whole text of what Prophet Mohammad
raised in said place thoroughly.

the shia claims that the prophet stopped in ghadeer ghom and told
Muslims that ali bin abi taleb is his successor in a very clear way
but the sunna either deny this or deny he says his cousin is the
successor they support this by other evidence like what happened after
mohammad passed away when ali ben abi taleb were a consoltant for the
three kalifahs before him (he was the 4th one) and he named three of
his sons abu bakr omar and Othman and if he did so he is not in
conflict with them. The shia believe of ali succession has
concequnces. The shia believe that God should choose successor and the
majority of shia believe successor of the prophet are 12 (they are
called shia twelvers ),the last 1 was born around 255H ( im given an
approximatation ) and he is alive till now  this means he is more than
1000 years old. Shia call successors of the prophet imams so there are
12 imams for shia  ?this is deferent than prayer leader the imam- and
ther are all chosen by god we have no right of choosing them the last
imam has disappeare so the leaders of shia like kamanaie in iran but
they are temporary leaders until he the 12th imam come back . some
shia also believe the sahabah did not listen to the prophet and have
chosen kalifah out of shoura ?negotiation ? the way abu bakr has
became  kalifah or  appointing  like omar or out of limited voting
like the way Othman has become kalifah. ( omar bin alkhattab says that
6 people has the right to vote he named them)  then after Othman
passed away the population chose ali. So many shia believe many
sahabah are ordinary person and they do not respect many of them like
abu bakr omar and Othman and many others. I think the best thing to
know more about this is to see an Islamic society probably there are
one or more for shia and one or more for sunna in big states like
texas im just guessing.

If you are really interested in finding the whole text of what the
prophet said you have to look at the sanad of the headeeth. There are
defferent text for the same hadeeth.  you are getting deep there.  And
this is the whole point did the prophet actually said ali is his
successor or he didn?t. the shia and sunna have defferent ways of
looking at hadeeths

But be aware shia not only believe in ali?s succession but  they also
believe he did not do any mistake at all this is a very centralized
thing in their believe the same thing is true for the other 11
successors. And many shia believe  mohammad ali fatimah alhassan and
al hussain were created before the universe and things like this.

Let?s say you have made a research in this and you have concluded ali
is the right kalifah that does not makes from shia
Me for example im historically from shia ? means my parent are shia ?
but technically im not because  I don?t believe that ali and  the 11
imam after him never ever do mistakes.
Sunna do not believe that God appointed the 12 imams though they thing
they are good people.