so a bit of an update to this, I found a person in europe who did this a while back with a serial interfaced arduino (the freeduino max serial). They don't make the boards anymore, but NKC had had some PCBs for them, so I ordered a couple PCB and the components to build my own. Hopefully I can get it to work without needing a USB interface - I was reading up on it and i'm not sure it would work at all.
In the meantime I'm trying to learn to write my own library for this instead of using the existing. The existing one may work, but it's good to learn. Where i am at now is trying to figure out how to translate any data that the ECU sends back to something usable - particularly in the case of the data that is more than one byte.