First thing you should do if you want to start a project like this from scrath is to settle on a programming language (C for example) and probably also a graphics library (like SDL) and get familiar with those if you are not already.
The next thing I would do is make a list of stuff your game needs, e.g. collision detection, dialogue, map, movement, level file loading, menus, etc.
After that you can search the map on tutorials on how to do those tasks (e.g. if you don't know how a collision engine has to work in a top-down view).
When you got the basic engine working you can start creating actual content, like items, levels, characters, etc.
Also we have a shiny new place for discussions and requests like this now on gp32x.de:
http://www.gp32x.de/board/index.php?app=forums&module=post§ion=post&do=reply_post&f=5&t=57626
You can ask for help there as well post details about your project and get other people interested.
I know it is not very crowded yet, but the more people get sent there the better it will turn out in the end
Anyway, good luck with your project and don't give up easily
foxblock out