To change the mySQL root login, there are instructions in the mySQL installation docs. To sum them up...
1) get a terminal session going
2) log into a mySQL session
3) update the user table
4) use mysqladmin to "flush" security settings
I highly recommend reading the docs on this however. It goes into detail and also contains the explanation on how to fix it if you accidently lock yourself out. Although I have no idea why anyone would accidently mistype a password and lock themselves out of root user access. looks sheepish