LED flickering, in my experience, was earlier technology LED products. And it was annoying. Be sure to get the best bulbs you can find.
If you reverse the polarity, you will get nothing.
As far as I could figure out the polarity, without trial and error, is as follows: get a nine volt battery and wire/connect up the LED’s one at a time. When the positive wire is connected to the positive terminal on the LED, and the negative wire is hooked to the negative terminal, the LED will function. This will allow you will be able to determine positive and negative on the “bulbs”.
There are six (6) LED’s in the instrument panel. The LED’s are in three vertical rows, with an upper and a lower bulb in each row. The positive/negative terminals have to be in the same direction/sequence. As I recall, if one of the lights in the vertical row has incorrect polarity, neither bulb in the row will function. I am sure this does not entirely solve your question as well as a schematic, but you are not likely to find a schematic as this was not an issue for the OEM incandescent bulbs.
You will really enjoy the result here… the LED light is much easier on the eyes, and does not generate all of the heat of an incandescent bulb. You are likely to find some signs of overheating plastic from the years of incandescent bulbs. Every time you turn your lights on, you will smile.
Good luck with this.