Well, why didn't you say so?
IMO everything you need is here:
http://www.palmone.com/us/developers/
About halfway down the page, you'll find:
===========================
Create applications and add-ons for any Palm Powered device, including
licensee handhelds and communicators. This is also the place to learn about
the Palm OS platform and the strength of the growing Palm Economy.
Links:
Palm OS Developers
Getting Started
Platform Technologies
Tools & Downloads
Documentation
Support & Resources
Training
Certification
Developer Program
Resource Pavilion
===========================
BTW I found this in seconds with Google.
If you decide you still want to use C to write
your programs, we can help you with the (standard)
C parts. The platform-specific parts which I'm
sure will also be needed are not topical here, but
you can get much help with that from that same site.
Oh, that'll be fifty cents for the directory assistance.
HTH,
-Mike