How do I effect the page that a menu item redirects to?
hook_menu serves, among other things, to map paths onto callback functions.  Whatever function is marked as the page callback for that path will be responsible for returning a either a rendered string of HTML or a Drupal render array.  So, for your very simple use-case, you could do the following (assuming your module's name is bh_vendor):

function bh_vendor_menu() {
 $items['admin/vendor/auth-stripe'] = array(
        'title' =&gt; 'Authenticate Stripe Account',
        'description' =&gt; 'In order to receive payments, you must authenticate your Stripe Account.',
        'page callback' =&gt; '_bh_vendor_auth_stripe',
        'access arguments' =&gt; array('vendor administration'),
        'type' =&gt; MENU_NORMAL_ITEM,
 );
 return $items;
}

function _bh_vendor_auth_stripe() {
 return l('My link', 'my/path');
}


You could, in fact, define a block using hook_block_info() and hook_block_view(), then embed that block on your page by calling module_invoke('bh_vendor', 'block_view', 'yourblockdeltahere') but that really only makes sense if the stuff you're embedding is re-used elsewhere.  If it's only meant for this one page then you should stick the code to generate that markup in your page callback directly.

Another option, if this isn't for a module that's to be widely distributed and is only configuration for a specific site: use the Panels module.  You can create a panels page at a specific url (admin/vendor/auth-stripe) and embed whatever blocks/content you wish.  If you want it in code it is exportable and/or can integrate with Features.