Module development and code questions

now that the debate around version numbers for core has been resolved (it'll be 2-digit version numbers), i'm turning my attention back to the new system for releasing drupal contributions.

there are a couple of main issues in the queue with a series of patches that are getting us close to a working, final implementation:

http://drupal.org/node/83339
http://drupal.org/node/84706

however, the patches are all from before DruaplCon (where there were some good discussions about all this, and some suggestions for changes), and before the switch to 2-digits for core. in writing and thinking about the system over the past few weeks, i've hit a few new complications that i'm unsure how best to resolve. any input on the following would be appreciated...

release nodes that are pointing to the HEAD

in the new system, releases will be real nodes (http://drupal.org/node/83339). if you enable the cvs.module, each release node has a cvs tag/branch that is associated with it (http://drupal.org/node/84706). release nodes that point to a cvs branch (not a tag) get nightly snapshots packaged up, just like the current "releases" we get in contrib. if enabled, cvs.module will form_alter() the release node form to rip out the fields to specify the version #, and add a drop-down to select what cvs tag to use. the only choices would be tags on the project that have no releases associated with them. once the tag is selected, the cvs.module figures out the version # from the tag name. so far, so good...

I'm not sure how this is possible...

I've got a module to create various custom blocks.
When I set the array list to the value of the exploded $delta variable, I can output the value but it always tests as zero.

I've been trying to make a layout following this layoutguide but it wont work. It doesn't bring any changes in the code on the frontpage.

Here'r the code I putted in the node-flexinode-1.tpl file:

<div id="special_content">
<div class="image"><?php print $node->flexinode_1 ?></div>
<?php print $node->flexinode_2 ?>
</div>

Hello everybody, i'm new to drupal but i'm an old user of all the cms. I've just installed the module Private Messages for version 4.7 and i get one php error at the administration panel.

Cannot modify header information - headers already sent by (output started at /home/djmk/public_html/modules/privatemsg/privatemsg.module:1) at /home/djmk/public_html/includes/common.inc στη γραμμή 266.

I didn't change anything at the module's files.

Ps. I wish i wrote everything ok...(And sorry for my english!!)

I want to either create a new module or hack the current one to allow users to have a type/class.
Registration will have different options depending on the class of the user.
Different classes will also be able to see slightly different data in drupal.

Can anyone suggest some starting points?
Is there a module that does something similar? Is there a way to extend & override the built-in user module?

I've recently started to use Drupal and my experience with it have been very good so far. I like the thin core, the admin panel, taxanomy and the modules available(such as taxonomy_menu and adsense etc).

However, there's some modules that I need but havn't found yet.