Upgrading Mysql
New servers will already have mysql 5 installed. But if yours does not, you can install it with the following steps.
# Shut down the current version
/sbin/service mysqld stop
# Remove the current version
yum remove mysql-server mysql-devel mysql
# Install MySQL 5.0
yum --enablerepo=centosplus install mysql mysql-server mysql-devel
chkconfig mysqld on
# Start MySQL
/sbin/service mysqld start
mysql_upgrade
# Update the MySQL GEM
gem install mysql -- --with-mysql-config