"Multi-Level Category Dropdown" to work with current version

Hello and thank you in advance!

I bought the "Multi-Level Category Dropdown":
http://www.opencart.com/index.php?route ... on_id=7955

I have OpenCart 1.5.6.3. What would I need to do to make this extension compatible to my current version? Just some direction would be appreciated. I can post the two vqmod files if allowed?

Thanks!

p.s. There is no email in the readme file

a) It's a paid extension so please respect the developer work.

b) It should work on Opencart 1.5.6.3 even if it says that is compatible with 1.5.5.1 (if not...some small changes are needed)

c) try to contact the developer int the comments