OK so here is what I figured out. Don't know why it works this way, but I stumbled on it.
If the file was not open in any program, and I tried changing the default program to open it, it would not let me change the file type to open with.
But what I noticed is if I had the file open with the program that I wanted to use as the default, then magically, it would let me change the default program, in this case, to Open Office. I don't know why it behaves this way, I can just tell you it does. So after opening the program in Open Office, I was able to select Open Office as the default program, and then checked the "All" button to open all programs of this extension with OO as the default program. It worked like a charm.
I don't konw if this is unique behavior in the latest version of IOS (10.8), but it works just in case others are running into this issue.
Thanks for the responses.