My clutch was going out in my 2007 Mazda 3 5 speed manual. Or at least that's what I figured it was. It started only when it was wet outside or raining then got to where it was always doing it. I bought a clutch kit brought it and the car to this guy's shop. The car switched gears fine at the point. He installed the clutch kit and calls me saying it's in but the car won't move. He takes it apart then says the clutch was put in backwards. Then he says that the slav cylinder is bad. Could him installing the clutch backwards mess the slave cylinder up

 

I noticed you haven't gotten a response and your thread has been up for a while. I'm sure you've solved your problem by now. But normally no. But everytime I've replaced my clutch I've replaced the slave cylinder as well. Maybe the install of the backwards clutch could have really messed it up, causing the need for replacement.