Advanced Wordpress Programming - Change my existing code

I need to do the following: In a custom [login to view URL] post template tied to a specific Category, I have to do the following: 1. "Get" every image attachment that is ACTUALLY Inserted into the Post's the_content variable 2. Identify or find the last or final image that is actually inserted into the_content(), and inject a DIV with custom field data BELOW that images final closing tag (it is a </p> tag AFTER the image). 3. The DIV contains custom field data from the field "mangoid-content". I need this worked on and finalized within the next 2 days. I have an existing piece of code you may work from that already counts all the paragraphs in the post type and inserts the DIV after a certain # of paragraphs. I just need this re-coded to function as 1, 2 & 3 above.