Best way to get to the fill plug on the 6 speed automatic

Before anyone says look at the how to, I've done so and looked at my car then looked at the how to.

I've concluded that I will need to break my arm in three places and smash it with a hammer to thin it out.

I've done two drain and fill using the vent tube and put in the same amount back in that came out.

I just want to double check that it's in fact properly filled and not under filled as I am now tuned.

If I happen to overfill it, what the symptoms would be so I can keep an eye on it.

Edit: I've looked at the wis and it states to add fluid until it overflows from the plug so that's what I wanted to check.