wp_dropdown_pages default value

I would suggest, that you switch from “URl query argument” style to arrays. This is a “feature” that is more a left over on some functions that is only available for backwards compatibility reasons than anything else.

Here’s a reworked version of your current arguments:

wp_dropdown_pages( array(
    'title_li'    => '',
    'depth'       => TRUE,               // originally: 1,
    'sort_column' => 'menu_order',
    'child_of'    => $post->post_parent,
    'echo'        => FALSE,              // originally: 0,
    'selected'    => $currPage,
) );

Now I wonder how you managed to display that dropdown/select element when echo was set to 0/false and no echo/print was prepended to that statement. If you are just adding it to your template like this, you better set echo to TRUE.

From looking at the selected argument (and as you can read in the docs in Codex), this is the argument that chooses what element currently is selected. As you are setting it to $currPage, which I assume that it contains the current page slug, it shows you exactly that. To “fix” your problem, simply set it to an empty string ''.

About the first/non-selected value: You can set that with the show_option_none argument

'show_option_none' => 'Please select a page',