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that's might be a tough repair unless you are patient and focused. The shaft the goes through the brake and clutch pedal can get rusted up and bind the pedals together. If you are lucky you can spray some kind of lubricant up to the pedals and it will be okay. Most times you have to remove the shaft and manually clean and lube the parts up. It's not hard but there are a lot of things that you have to take off to get at the shaft bolt and get it out of the vehicle to take it all apart.
I think I would look at what the vacuum is doing there. Try pinching off the vacuum booster's vacuum line and pump the brakes and see if it still does it. (while you are in park. don't go driving like that. It will make it hard to stop)