You didn't say what year your 850 is, but here's the story on my '97, other years may be different:

You have to remove the center console to get the switch assembly out, it is installed from underneath.

Those switches are all soldered together with metal strips for the connections, so disassembling the unit is a royal pain.

It is possible to pry the rocker off the switch from above and clean the switch, but this procedure has a high failure rate, and it's easy to damage/mar the plastic rocker and lose bits of the inside of the switch. Reassembly isn't all that easy, and this may not cure your problem even if it goes OK.

I recommend you just purchase the switch/harness unit and replace it. It's about $150 from the dealer.

Mike