If you found something that allows you to control Winamp (a DLL in other words) then you are all set. You simply create some kind of trigger, together with some form of access levels, make an on text event like:

on winamp:text:!control &:#mychannel:{
if ($2 == next) <call dll to move to next song>
elseif ($2 == pause) <call dll to pause song>

This uses a named userlevel "winamp", to understand what this implies, take a look at /help user list