upgrade/instal/uninstal packages linux box safety issue

Hello Group,

Could some one tell me how safe it is to upgrade/uninstall application
level packages i.e libxml2,
libxlm-dev. I have libxml2-2.5.20, for a Kannel (a WAP gateway)
package I need a libxml2-2.6
package.

I read somewhere that it can be unsafe if a package is
upgraded/uninstalled from the original
distribution of Linux.

I am seeking some expert advice. Without upgrading the package my
Kannel won't work on my
machine.

Please advise.

Thanks.

arun