MediaWiki Table of Contents - Use CSS to: Scroll not working or being overridden

Question

Currently using MediaWiki and the MediaWiki:Common.css to configure my Table of Contents.

As of now, I've floated it to the right and it moves as the user scrolls. I've found documentation, but cannot properly implement the code to change the ToC's behavior. I left the default CSS code there and added the following code to the bottom:

body #p-coll-print_export {display:none}
#footer { display: Lastmodifiedat; }
body { font-size: larger; }
#toc {float:right;margin:0 0 1em 1em;position:fixed;top:150px;right:10px;}
#toc {| style="max-height: 1000px; overflow-y: scroll;"
...
|}

This is one example of attempting to implement overflow to scroll, but the ToC still does not scroll.

Lastly, I got the transparency until your mouse hovers code from another site, but cannot get the code to work on my end. Code below:

.cFloat:not(:hover) {
    opacity: 0.65;
}

.cFloat:hover {
    opacity: 1.0;
}

Aside from incorrectly implementing code into my own CSS page, I cannot find specific causes to it not working. Any help is appreciated.