Have a quick read through the docs on plugins here. Then have a browse through the available plugins here. As mentioned in the docs, the easiest way is to install them automatically from the actual plugin page (if it works). Also common thinking is "less is more" to minimise potential issues. That said we tend to have 70+ on our install ... but we like "playing" and have the capability inhouse to get ourselves out of trouble when necessary.
As for being old, we're all getting there and it certainly sneaks up on you; I guess the alternative to getting old isn't that good an option either