[MOD]On Klick Prev / Next Images - implementation needed

[Jackomo]

Hi,
I understand that following the excellent description of

http://www.4homepages.de/forum/index.php?PHPSESSID=09627b2b6acd323dfd47f77da11fd8ef&topic=24167.msg132459

should make it easy to implement the mod.
However it doesn't work for me. Maybe it is because I really messed things up, or it is because there have been made modifications to the files already.
As I really have no clue of coding, I just can cut/paste, thus I can't trace down errors, I'd like to have somebody implementing this mod for me.
Of course  nothing is for free 
If you want to do this, let me know how much $$$

Of course I can grant you access to the files

Thanks
Jackomo