to add/remove stuff to/from the fluxbox menu, use the tool FluxMenu, that is found when you right-click the desktop with your mouse, then select Fluxbox-menu -> Tools -> FluxMenu and just use it
the tool lets you add and remove, edit and re-arrange all the menuentries, and after you're ready, save your changes and use them.
uninstalling programs depends on your distribution, not fluxbox...so it's a bit different thing if you use Fedora, than if you use Gentoo. what are you running?
and sound..that too depends quite a lot of what distribution you have. first of all, do your apps do anything (like error msgs) when you try to use sound? for example, if you open Xmms and play a song, will it start "playing" (but without sound) or does it tell you that no sound is available?
and the keyboard...edit (with some text-editor, root mode required I guess) your /etc/X11/XF86Config like this: find the Input Devices -section, and there is some info about your keyboard. here's some of my file:
Option "XkbRules" "xfree86"
Option "XkbModel" "pc105"
Option "XkbLayout" "fi"
those tell my X what kind of keyboard I use. when you need to change your keyboard's language, just change the XkbLayout, and (I have finnish, so it's fi) change the given option into what you need (se). that should do (for X, console needs another type of edit).
EDIT: of course, after editing XF86Config you need to (re)start your X to get the new options work