I guess this is a lost cause

I'm really trying to find out the troubles of this mod but freaking stuck! Is there a global reference chart for the new vb4's variable etc etc??
I know i'ved seen a few changes that were made in V4 for some strings or so like this one i thing should be modified to accommodate the new version
Code:
if($dothumbnail)
should be replace by:
if ($_REQUEST['do'] == 'not sure what to write in here')
etc etc etc
There's a few options that i would like to add to this mod, like, in the posbit_quickreply, adding the edit box to change the thumbs but when i add the code for it in the template, it doesn't show anything as it doesn't seem to hook to the plugin's function.
Anyway, a lot could be done but i'm a freaking newb with this part
I'm not a coder but trying to understand how it should work.
If anyone could give me a hand i would appreciate a lot
Cheers