There is indeed a plug at that location. But the TIS points to a different 8mm hex fill plug at the back of the trans for fluid fills. Here is the TIS link:
TIS trans fluid fill
Now that said. From what I can find EVERYONE, and I mean everyone, uses that fill plug you pointed out. I guess I'll go ahead and do that as well since it is A LOT easier to get to. Plus, then I can rehang the exhaust and I don't have to find out what an open header N52 sounds like.