بسم الله الرحمن الرحيم
If you pronounced verbally the Kalimah Shahadah and understood it and testified it by your heart then you became a Muslim. It is not a condition to accept it in the presence of any Alim or Muslim. The meaning of the Kalimah Shahadah is as follows:
I bear witness that none has the right to be worshipped except Allah, and Muhammad is the Apostle of Allah.
Now you should start learning salah and other things. Keep on learning it gradually. As far as changing the name is concerned, if your name does not have a bad meaning you may continue it. However it is better to select any good Islamic name from these names: Abdullah, Abdur Rahman, Abu Bakar, Umar, Usman, Ali, Jafar etc. You may keep your old name in the papers etc and let people call you with your Islamic name.
Allah knows Best!
Darul Uloom Deoband