If the PIX 506 is covered under a maintenance contract, you can download the latest version (6.3.4) of the PIX OS and perform an upgrade via tftp.
A good configuration utility would be the PIX Device Manager (PDM). PDM is a web-based interface to manage the PIX. This would also be available if the PIX were under maintenance. PDM becomes available with PIX OS 6.0.
Here is a link to the documentation for the PIX firewall. You will find the documenation for both PDM and the OS. You will also be able to find the configuration documentation for PIX OS 5.2 through this page as well. It will at least allow you to configure the PIX via CLI.
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/index.htm