Maybe that's all it is after all. I can dig around the FSM a little later to try figure out the trans+component compatibility matters.
Is the 03 q45 located close by? Maybe you could just look at the trans plug to know what kind of work to expect. I'd say if the trans plug is different, then we're looking at pulling the entire engine control harness from the ECU back. Not too terrible of a job, but a headache anyone could do without.
This is the 06 m45 trans. The first year had maybe 3 plugs in place of this one, and the 06 q45 trans I saw on ebay seems to be similar to mine. I have no idea what an 03 one looks like, but this is what you want to avoid.
I am located in Belleville, IL so if the stars align I could swing by and take a look.