This is an older pic but not much has changed other then that square box being gone. and that BX being fed from the top.
The bottom part of that panel is the access for the main lugs, and the side is full with wires. I do want to install a bigger panel, so am I better off just waiting and doing that then feeding it properly? The gas line also enters just above so the meter is there, which would be in the way, so it's easier if I run the conduit past the meter and to the other side. But that's minor details, I can try to figure a way to compromise so I can get the conduit to the right side of the panel. I know I can't turn more then 360* total so I have to keep that in mind.
Come to think of it, that doorbell transformer can go, though the hole is only like 1/2. I'm guessing I will need 1 inch conduit for a 100 amp service. Could I actually use my dremel to make the hole bigger? This would make the edges very sharp though, but guess the conduit itself would be entering so is it really an issue? I never connected a conduit to a panel before but I'm guessing it's a fitting I'd find at HD where the conduit stuff is?