The source distribution of MySQL does come with an example init script, doesn't it? Copy it to /etc/init.d/, make it executable and create the symlinks to it in the rc.? directories according to on what runlevels you want it to be started or shut down.
Yup, you should have have a file msql.server somewhere if you installed from source
cp that to /etc/rc.d/rc.mysqld
chmod +x rc.mysqld
if it ain't already
Should start at boot now aswell as /etc/rc.d/rc.mysqld stop/start etc.