This may be a dumb question but I'm not that familiar with the Linux desktop...
Can I run GNOME apps on KDE and vice versa?
For instance: As I understand it a app called K3b is a cd/dvd burning app for KDE. Can I use K3b in GNOME??
Yes, you can. I would normally add a proviso along the lines of "providing you have the KDE libraries etc. installed" but yum/rpm/apt etc. dependency handling should enforce that, so the short answer is "yes".
Paul.