Creating a plugin could use some advice…

Well 1st I need a link to a good walk through on building a proper plug-in for WP…

I am hoping to add a plug-in with a settings page on which you could build a custom message for the dashboard…I have seen a few notepad plug-ins and such floating around but not exactly covering what I would like to do. I would like to have the actual message creation/edit portion on a settings page so the dashboard just adds my message just like the other screen option boxes. I would also like to filter the message by user level so on the settings page we would have 3-4 text inputs for the different levels so a subscriber wouldn’t see the message meant for an admin or an author a message for subscribers and so on.

Any pitfalls I should be aware of?

Seems like this would be easy enough any advice to get me started or point me in the right direction would be much appreciated!