HI.
There is no major risk in upgrading, but it is recommended to do it before "going online".
The thing is that it is not only an upgrade for the pix itself, but for the administrator also that needs some time to experiment and learn new features and commands like
access-list, PDM, and other.
It is also recommended to get the DES activation key before the upgrade, so you can install it during the upgrade process.
The DES key is required for PDM, IPSec, SSH and other features, and can only be installed during pix os install process.
For this you need to send the "show version" output to your CISCO dealer.
Therefore I recommend that you do the upgrade first, including DES and PDM install, do some more tests, and then go online.
Bye
Yizhar Hurwitz