This is quick guide howto change runlevel on GRUB2. Same method of course works, if you want to change runlevel from 3 to 5, from 5 to 1 or from 3 to 1, etc.
Runlevels
0 – Halt Shuts down the system.
1 – Single-User Mode Mode for administrative tasks.
2 – Multi-User Mode Does not configure network interfaces / services.
3 – Multi-User Mode with Networking Starts the system normally.
4 – Not used/User-definable For special purposes.
5 – Start the system with display manager. As runlevel 3 + display manager.
6 – Reboot Reboots the system.