I doubt it will have any nasties.
In the App Store icon, it should tell you if there are any updates needed.
The disk utility, under launcher, should allow you to check the health of the disk partition and allow you to repair it if needed.
I have Ccleaner for OSX installed that allows me to clean the crap (funny that) off my MacBook Pro, only really cache type crap. It doesnt to reg type fixes like the wondows version allows.
good luck
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