In most cases it's 4mm hex for the torque converter and pan drain plugs, 8mm socket or wrench for cover panels.

Ramps will do fine.

Paint a line on the crank pulley visible from above when the torque converter plug is at its lowest. Next time you change fluid, you can turn the engine from above to locate the drain plug.

How about Mobil 1 ATF instead of additives?

Sixto
93 300SD 3.0