I've been using it for years; just download and install the apk from the website like any other side-loaded app. Yes it modifies the original youtube app, replacing it. I've never had an issue with the main app updating and breaking anything. Updates to revanced have to be applied manually the same way as the original install, but I've been super lazy and gone several years at a time without updating at all and I've never had an issue.

I used to run the original vanced app the same way; rarely if ever updating. It just hasn't been necessary. Hell, the only reason I'm not still using original vanced app is because the device it was installed on has a broken screen.

Revanced is essentially the same app as the original youtube app with all premium functionality; but with adblock, sponsor block, and a huge host of toggles to show/hide almost every part of the UI or modify the apps behaviour (things like fixed quality settings instead of just 'auto' or a default playback speed).