easiest way to edit sidebar?

You could edit the sidebar.php file, right on your computer’s hard drive.. then re-upload the file to that theme’s folder, in the FTP directory..
wp-content/themes/that-theme-folder/

Or, CHMOD that theme’s files 666, via an FTP client. Then you can edit it via the blog control panel, at: Presentation => Theme Editor.. I hope this helps. ??

spencerp

any 3rd party plugin to manage all this without looking at all code?

Widgets? If your theme supports it…
https://automattic.com/code/widgets/