change data dir on mac (no replies)

I just installed mysql on mac leopard using mysql pkg
everything works but now i need to understand few basic under the hood
I create my.cnf under /etc/ and I expected to be able to change data datadir from /usr/local/mysql/data/ to a different folder but it didn't work
First of all /usr/local/mysql/data/ is owned by _mysql user and I cannot even browse it
I tried to copy the folder to /usr/local/mysql/databases/ changed dir ownership to root so i can see the content, but If I set datadir to new folder /usr/local/mysql/databases/ mysql does not even start

to start mysql I'm using MySQLCOM installed with pkg file

is there any realtion between MySQLCOM and data dir owner?
does MySQLCOM start mysql with a specific user and if yes which one/where is that user defined?

thanks for any help and sorry for the confusion, but I'm really a newbie!!