I would have helped, but I hit too many roadblocks and gave up.

Among those were:

• The Eclipse project tree that I was referred to contained absolute paths that were not present on my machine.
• The list of steps to set up Eclipse for plug-in debugging was slightly wrong. I was unable to figure out what exactly was wrong.

The Getting Started on Hibernate Tools page of my dreams would look like this:

It would start assuming the programmer has Eclipse freshly installed.
It would give the steps to follow to install the plugins needed for hacking on Hibernate Tools, assuming the programmer is starting with any of "Eclipse IDE for Java EE Developers", "Eclipse IDE for Java Developers", or "Eclipse Classic 3.6.0".
The next step on the list would be a pointer to the download location of a self-contained project, ready for File -> Import... -> Plug-in Development in Eclipse. In fact there should be two such projects, one for the bleeding edge (to actually work on the plug-in), and one for the latest stable release (for diagnosing problems reported by people who just use Hibernate Tools).
The last step would be a short walk-through through a debugging session, for those who haven't done Eclipse plug-in hacking. Such as setting a breakpoint somewhere in the Eclipse Tools code and starting a code generating run. (I guess such a walk-through already exists somewhere in the Eclipse PDE docs, linking that should be enough, possibly accompagnied by caveats and a short FAQ list.)

Total effort to set that: a couple of workdays (mostly to trace all the steps that are being described, and to set up the list of Eclipse plug-ins needed to turn it into a PDE environment).
Much less than a week unless there's a roadblock. (Note that you're more competent to resolve any roadblocks than Random J. Volunteer.)

Just my 2 cents, in the hope that it will answer questions you're having.