How to batch update post content with custom post meta value

Question

I have a custom meta box, using WPAlchemy, in which I am looking to get rid of. However, I would like to get all posts that have a specific custom meta value set, and insert it into the begininning of the post content, then delete the meta value.

I have a feeling this post gets me close, as I have been able to successfully add content to the beginning of posts, but have been unsuccessful accessing and adding the custom meta value I'm after. I'm also a little unsure of when to hook into WordPress and perform my actions.

Anyone have any suggestions on the best way to go about this? I figured I would build a simple plugin, activate it, let it do it's job, then remove it.