Well no, your plugin directory is just that, a directory. It's probably a good idea to have at least 1 more browser installed, just in case you run into some problems with the other. Mozilla is about as standard as it gets so I'd go that route if you decide to.
Anyway, to install plugins in konqueror, click "settings" then "Configure konqueror". No click the very last tab there "netscape plugins". This is just going to search the default "netscape plugin" directories for plugins you have installed, it's not dependant upon having netscape installed though, but simply follows the standard.
So to find out how to install plugins for netscape/mozilla/konqueror:
Your mozilla plugin directory is going to be something like:
And then follow the instructions from that site. Then once you have done that, click "Scan for new plugins" in konqueror.
If it finds it good, if not, simply manually add the directory:
to the list of directories to check, then click the "Scan for new plugins" button again.