How to remove the dask - Buick Lesabre 1997

I have a Buick Lesabre 1997, Limited edition. Could someone tell me how difficult is it to take off the dask to remove the instrument cluster ?
I had an intermittent problem with speedometer, the needles jump all over the place, problem and last for a short period of time. When a hit the dash with my hand, the needle jumps up and down, is it an indication of problem of connection ?
One person advise me to check the ground and to verify the printed circut board. Does someone have a schematic diagram to remove the dash ?
Any help will be appreciated.

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