It depends on how large your program is, and how much it made use of the hardware. You'll probably need to update pin assignments in your hardware, and update to Dynamic C 10.72 which adds some new features:
- support for "far" (32-bit) pointers
- "const correctness" in function declarations
- support for ANSI C90 features and a more-complete Standard C Library
You might want to review section 2.2 of the User Guide (http://ftp1.digi.com/support/documentation/019-0167_L.pdf) and make note of the additional ANSI C features.
And section 2.3 discusses some of the other changes from Dynamic C 9.