Ok, let's clear a few things up shall we?

Yes, I've taken more than 5 mins to look at what's involved fitting a windscreen, and no, I've never paid anyone to fit one.

Sierra windscreens are bonded. And they are bonded exactly like modern cars. No difference. And as with all bonded windscreens, you do need a cutting tool to remove them. It doesn't have to be powered, but you need to cut them out. Beit with a wire, or a knife.

The fact you aren't a pro, I suggest you don't attempt it. And no, you don't pop the screen out of a Sierra. You pop the screen out of a mk3/4 Escort, but not a Sierra (because Sierra's are direct glazed, and mk3/4 Escorts are indirect glazed)

I've fitted both IS200 and Sierra screens, among the other 12-15,000 windscreens I've fitted over the past ten years. So yeah, I know exactly what's involved, and is why I'm qualified to say you are talking absolute shite. The IS doesn't have numerous rubbers (the actual term is trim - rubber is the term you apply to indirect glazed screens, such as the mk3/4 Escort, that is held in with a rubber), and the Sierra doesn't have just one - it actually has two; inner and outer. Here's a top tip for anyone restoring their Sierra - the inner trim is actually the same as the inner trim from a mk3 transit, so if you need one, go rob it from an old Transit). Both the IS and the Sierra need the outside trim removing, along with the scuttle and wipers, and you should remove the inner trim on the Sierra too, so as to avoid cutting it with a wire or knife. Add to that the scuttle on a Sierra is rubbish, and the clips the screws fit into nearly always break, I'd actually much rather do the IS. Also, you say the Sierra has much more access once you've removed the trim - also wrong. There is more space between the glass and aperture on an IS than a Sierra.

In terms of fitting, you have to be much more accurate with a Sierra screen than you do an IS - this is because of it having two trims; the "space" for the glue is greatly reduced. You want to maximise the contact area on both the metal aperture as well as the glass screen, and this is hampered by having both an inner and outer trim. So many Sierra's I go to, that have been done before, have too much glue, and it splurges onto the trims, meaning they tear coming out. Or they have too little glue, as the fitter is conscious of the double trim, but that reduces the glue to surface contact. Not good.

Then there's your statement about the screen in the IS (and I'm assuming you're also generalising about all modern cars here too) being bonded to more of the car than a Sierra - absolute absurdness and utter garbage. All windscreens are bonded the entire way round. The bonding process for a Sierra is exactly the same as that for an IS200, or Audi, or BMW, or Bentley, or Porsche, or Ferrari, or Nissan Micra.

So next time you wanna get arsey with someone on the internet, and call them a "keyboard warrior", why not actually check your facts, rather than spout off complete and utter shite about something you clearly know nothing about, but still put across as fact.