I have never heard of anyone taking the multi function switch apart to fix it. They are pretty reliable, mine is original and works fine. They are expensive to replace unless you get one from a bone yard. I think people attribute problems to the switch that might be something much simpler to fix. These cars are very complicated electronically speaking, diagnosis requires testing, so that you don't replace parts unnecessarily and spend more money than you need to. Make sure your problem is the switch and not something else/simpler. That requires the FSM. It has trouble charts to isolate a problem.
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98 Riviera SC3800 All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU