A .PRC and .PDB are "PalmOS Databases". What's in a PRC is mostly code and supporting things like screens, bitmaps and such. It's very rare to find firmware inside a PRC. For example we support field firmware updates but package the firmware in .PDB files that the app can read and use.
Be aware that a non-programmer may be very upset working with this stuff. I don't want to offend anyone but all this is going to take a seasoned programmer. One that has written code and apps for embedded devices to de-code the .PRC. I do not know of any friendly tools to decode a PRC.