If you don't want to mess in system files manually, install Titanium Backup and you can remove any apps you don't want with it.
You'll need to be rooted either way. (Certainly for TB, pretty sure for manually as well).
And no, a task manager is largely unnecessary. Apps never really need closed. If they aren't using CPU, they are doing no harm. And if they are using CPU, it's because they are doing something in the background e.g. downloading files or something. Either way, you don't want to kill them.
The only time a problem arises is if there is a bug in an app causing it to use CPU when it's not running. In this case, restart your phone. If that doesn't fix it, consider uninstalling the app and seeking an alternative, because there is clearly a problem with it. Otherwise, just kill it manually every time after you've used it (if it restarts itself automatically, definitely get rid of it)