Step 1 can be accomplished (I believe) with the following code:
function override_bp_core_settings_nav{)
remove_action('wp', 'bp_core_add_settings_nav',2);
}
add_action('init', 'override_bp_core_settings_nav');
add_action('wp', 'YOUR_SETTINGS_NAV',2); // this is where you would add your new nav
This is untested, but hopefully it gives you some pointers.
