alright, I have your solution:
go and create a new php file called mywiki.php or something like that, whatever you want really. inside the file, paste the following code.
<?php /*
Template Name: Wiki
*/
?>
<?php include "header.php"; ?>
<div id="container">
<div id="topcontent"></div>
<div id="singlecontent">
<div class="clearer"> </div>
<div class="singlepost">
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<?php the_content(); ?>
</div>
<div id="bottomcontent"> </div>
</div>
</div>
<?php include('footer.php'); ?>
Depending on how you added your wiki before, if you added it within the write pages, then you should be able to do the same thing here. Otherwise, you could take your wiki code, and paste it within the <div class=singlepost>
I believe that this should work for you.