There are 6 4mm allen headed bolts one he end of each spring post, to change springs simply undo all 6 evenly in a criss-cross pattern then remove bolt, cap and spring and replace with stainless, doing them up again in a criss-cross pattern.
Not sure if there is a torque for them but they are so small just do them up till u feel resistance as they can easily snap
Mine was only out for one day and the springs corroded
when i started it up rusty water was flung all over the bike