faded and yellow decals

can someone please tell me if it is possible to fix yellowing decals by placing them in a window to allow the sun to fix them

Yes it is. Place the decals in a baggie, then tape the baggie on a window that gets alot of direct sunlight (decals facing outward). Leave them there for a couple of days.

[bow] thankyou very much for that

You are welcome. That trick saved the decals to a Zero I’ve had for a few years. Just finished it. Worked well.