you should be able to remove that torque limiter they normally have 2 screws, undo them then remove the spring and lock the gearbox using grub screws - the tutorial you mentioned im sure will cover this in more detail

the batteries if your talking about the drill batteries those wont be much good but if they are new should hold they charge (bearing in mind they will be 1200mah cells, ie not very high in robot uses)

if you have an itelligent charger then you could try and cycle them but it probably wont do much for them, upgrade now and save hassle later......and dont put them in the fridge.........never ever heard that idea before