Here is what I do. All of these instructions are based on my minimal experiences with working PACs, so YMMV.
Download your pac file via your pac URL. It's plain text and should be easy to open in a text editor.
Near the bottom, there's probably a section that says something like: return "PROXY w.x.y.z:a" where "w.x.y.z" is an ip address or username and "a" is a port number.
Write these down.
In a recent version of eclipse :
At this point, you should be able to browse using the internal web browser (at least on http URLs).
Good luck.
Edit:
Just so you know, it's WAY easier to use Nexus, one set of <mirror>
tags and a single proxy setup (inside Nexus) to manage the proxy issues of Maven inside a firewall.