So I've been asked to take over another persons code in WordPress with little time before launch date... Usually I would say no but it's an interesting project. I am a pretty good Drupal programmer but have little experience in WordPress.
So I want to know, what is the difference between developing a Drupal module and a Wordpress plugin / widget? Are the systems sort similar? API's, hooks etc? Could you learn to do it sort of good in a week?
If you're a good Drupal (and PHP) programmer I'm pretty sure that you can pickup Wordpress programming in a week. The trick in such a scenario is a to pickup a good book/ebook that gives you the basics so you don't have to google around for the absolute fundamentals. After you've picked up the basics I think its just about writing decent PHP code, checking out the code of other (similar) modules and checking API references.
Here are some links (though you can probably google it for yourself...) http://codex.wordpress.org/Plugin_API
Some lessons http://codex.wordpress.org/WordPress_Lessons
Books on wordpress https://www.packtpub.com/books/wordpress
You might particularly want to checkout https://www.packtpub.com/wordpress-plug-in-development/book