Funnily enough I spent an hour yesterday re-soldering the neutral wires on my 96SL.
Easy enough, just run the rubber cover back up the wires (which you've disconnected further up), and use a ring/open spanner to unscrew the switch from the engine casing. Just be careful when unscrewing that you don't break the wires off. The wire cover tends to trap rain so they're nice and brittle at the bottom...
The switch can stick a bit so WD40 the hell out of it and give it another go. I've also seen recommendations that you leave the washer off when re-screwing it back on the engine to give it an extra mm.
If the wires are broken then you'll need to heat the little barrels where the old wires is with a soldering iron and pull the old ones out, the re-solder it.
Good luck,
Ali