Although the clutch hydraulic system as well as the brake hydraulic system share the same fluid reservoir if you are just replacing the brake master cylinder it won't affect your clutch, you should be a little careful though.

The actual plastic reservoir is pressure fit into the brake master cylinder. When you pull your old one off you have to be careful of the rubber line that sends brake fluid to the clutch system. It is attached on the right side if you are facing the enginebay. It is fragile at this age and honestly should be replaced if it hasn't been in a long time. But if you are careful you should be able to not disturb that line. Then the rest is pretty easy.

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