I could not find information about the wire colours and positions for this machine so I made a very short video. I think the same wires colurs are used on many similar machines of the same era. I have not shown how to dismantle the top plastic cover of the unit.
When you remove the switch the wires will try to scrape off. Take care and you may be lucky enough to get them out. If you cant you will need to fish them out with a piece of bent wire or take the top cover off to get a better look at the wires. They are near the bottom of the machine so you wont have great access to them even with the top off but it may gave you a better view.
The switch had plastic springs on each short side. You lift up the end with a small screwdriver then push the plastic bars. Wriggle the switch out.
Best of luck.