Perhaps look into something like TIS2000? That's GM proprietary stuff, so you probably need their software to do anything with it.
Is there any way that the above file type can be opened to view its contents?
I have opened it up in a hex editor and it all apperes to be encrypted.
Does your hex editor have a feature to create a histogram of the character distribution? If the file is encrypted it should be completely flat. You should also check out binwalk:
Sometimes a compressed file is embedded with padding and you can carve out the original. If both of those fail, it still just might be XOR'd. Look for repeating strings in what might have been empty space in the original.
I recently figured out how to extract binaries from ford phf files. They are in a format similar to Intel .hex. Often developers opt to simply make a file look encrypted, rather than actually encrypt them. Especially since the keys must be distributed anyhow.