Islam accept anyone as long as he/she believes that Allah is God and that Muhammad and all the others prophets are His messengers. Than after it come the learning process of whats wrong and whats right.
All sins committed before coming to Islam are forgiven. No matter how bad they were. They are forgiven. One who converts to Islam is totally reborn and starts with a clean record.
Amr ibn al-Aas said: When Allaah put the love of Islam into my heart, I came to the Prophet (peace and blessings of Allaah be upon him) to pledge my allegiance to him. He stretched out his hand towards me, but I said, I will not pledge allegiance to you, O Messenger of Allaah, until you forgive me my previous sins. The Messenger of Allaah (peace and blessings of Allaah be upon him) said to me,
O Amr, do you not know that Islam wipes out whatever sins came before it. (Narrated by Imaam Ahmad, 17159).
Of course, Allah knows what in the hearts of humans so if someone is converting while he still has the intention to stay as he was, than the hadeeth doesnt apply. The hadeeth applies to those sincere in their repent, sincere in their accepting of Islam.
You must know, may Allah preserve you, that Islam doesnt make any difference between races, colors, languages and thats why the prophet peace be upon him said in his last sermon in his last Hajj:
you know that every Muslim is the brother of another Muslim. You are all equal. Nobody has superiority over other except by piety and good action.
And in another hadeeth that I wasnt able to find in english ( I have hard times finding the translation of the hadeeth in arabic I learn so I apologise) ; the prophet pbuh mentioned that theres no difference between an arab and non arab , a black and a white except by piety.
You can also read the last sermon of the prophet peace be upon him here, one cannot get enough of rereading it:
Last Sermon of Muhammad (Peace be upon him) (check the footnotes too , it might interest you)
I hope what Ive said will be of benefit Inshallah