1999 Cadillac STS Oil Pan Gasket

I attempted to remove the oil pan, but could not get to one of the bolts because of transmission (could not fit socket head squarely on bolt), This bolt is different than the regular oil pan bolts (13mm instead of 10, on corner of pan between tranny and crossover pipe), but looked like it needed to be removed to get the oil pan off. First question is whether I was wrong about this; do I leave that bolt in?

If the trans. Does need to be removed, then my next question is whether I can just allow the oil pan gasket to leak without doing further damage to my car. My thought is that as long as I keep enough oil in it and the oil is just dripping to the ground, I should be fine, but let me know if I'm missing something.

Also, I am assuming the leak is from the oil pan gasket because that's where I see the oil (on the oil pan and directly lateral from the gasket; nothing above). Am I overlooking something else that could be causing this?