I´d like to change the syle css of a few of your plug

Hi
I´d like to change the syle css of a few of your plug in, so i supose that i have to change the css style sheet from this plugin on its respective folder wp_comtent/plugin/css. That is correct. isn't it?

But i have onether question. What happens if i update this plugin? everything remains the same, with my changes unaltered, or i have to do it again? or is another way to do things?
Thanks very much