Any window fitted in the last 10-15 years will use double sided glazing security tape to hold it in place (so it doesn't matter if the beading is external). Before you start, look at the thickness of the foam tape, because you will need to buy a roll of the tape to refit the window, and it's available in many different thicknesses. You probably want a couple mm thicker than it appears so it's compressed when fitted. Also available in black or white, but black is most often used so it doesn't show when it gets dirty, as you can't really clean it.
You will need to cut through this foam all the way around before the unit will come out. You will also need to clean the remains of the tape off the frame and glass before refitting.
Also I would suggest getting a couple of glass rubber sucker handles for handling the unit in and out of the frame. Cheapest source of these are sold as temporary shower cubicle handles, often for under a fiver each.
If you have leather gloves/gaunlets, use them too, particularly if there's any risk of the glass falling apart or if it's already cracked, and the larger the sealed unit, the more important that is, together with thick long sleaves/coat and thick long trousers, which might help save you from serious injury.
When you lift the unit out, be very careful not to knock the corners or edges on anything hard. Even a light brush against a brick or concrete can cause a toughened unit to shatter - the larger the unit, the more likely this is. Stand the unit on something soft and lean it against something soft (such as timber).