I recently removed the rear windows from one golf and fitted them into another, I would say you definately have to have access to the inside of the glass. To get them out you need to pull the seal down round the top corner of the window and apply pressure from inside. To refit the glass you need to thread some thin rope around the inner lip of the seal then have somebody apply pressure outside the glass while you slowly pull the rope out around the window to pull the seal into the bodywork. I imagine the only way to do it from outside would be to use a sh!t load of lubricant (e.g. washing up liquid) but you still wouldn't guarantee getting the seal back in properly and with the look of those subs you'd blow them back out in a second!
