Change run level

Good day!

• If a RHEL server at run level 5 is switched run level 3, will that interrupt already running applications, like MySQL for example?

We have a RHEL 5.9 server which is running in init 5.
The gdm-binary command is taking up 50% of the CPU.

Not sure why this was ever started at run-level 5, but I have already updated /etc/inittab so it boots to 3 in the future.

My concern now is if I 'init 3' the server to stop Gnome, will the MySql instance hiccup?

Thoughts and Thanks!