Module development and code questions

I'm developing an online quiz program. I'm debating whether I should roll my own or extend drupal to add this feature. Extending drupal is more attractive because alot of upfront work is done for me.

I have a hook_user function in my module, in which I create some fields with values. As a result this creates entries in the users table for the parameters created.

How do I delete these values from the database?

Is anyone working on updating project.module for Drupal 4.5? And what about the version of Project being used on drupal.org itself? And will there ever be a point where the system is customizable away from software releases and more towards general project use -- a website project doesn't need a license or patches for example.

How can I tell what the active node is, or more specifically what the category is of the active item? I tried a global $node, but it didn't seem to be available.

help!

There are a bunch of great mods out their finding more ways for users to get content. I think the workspace.mod and mypage.mod views are great and am looking forward to trying out sections. There is also books (in core), series, and articles- not sure how they are all separate. I'd like to find ways for users to relate to content better. More like a friendster type trees where you can see how users are related, how their posts are related to topics-vocabs, etc. Then it would be great if users could create views for others to see.