setting up mod_proxy - plesk, apache, .htaccess?

I want to set up mod_proxy to work so that my blog is running under a subdirectory of my site rather than subdomain so i get the seo backlink benefit.

What im looking to do is get my tumblr blog which is running at blog.mysite.com (which is in turn mapped from myblog.tumblr.com) will be running on mysite.com/blog

How can i set up mod_proxy to do this, is it just something that i can setup from inside of my .htacess file ?

Ive got my site hosted on an apache server, using plesk as a controll panel.

I contacted my webhost and they told me mod_rewrite could acheve it, they gave me this but said they wont provide me further support regarding mod_rewrite as its somthing they dont support

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} ^example.co.uk/blog$
RewriteCond %{REQUEST_URI} !/standard
RewriteRule ^(.*)$ http://example.tumblr.com$1   [R]
</IfModule> 

ideally id like to use the mod_proxy method as it recomended from an seo point of view from this article http://www.seomoz.org/blog/what-is-a-reverse-proxy-and-how-can-it-help-my-seo