I have a suit which has a hole in one of it's sleeve. Most of the time, the suit was stored in a dark place, which unluckily was also the reason for the hole. Is it possible to replace a whole sleeve of a suit, or will a new sleeve, due to the natural bleaching by the sunlight on the rest of the suit, stand out?
If you have a good clothing repair shop, they might be able to stop the hole like people used to stop socks and well done it is almost invisible.
A replacing sleeve will almost never work, even when it matches very closely when new, it will likely react different on aging and on creasing and dirt.
A good stop is as good as invisible, but it is very hard to do and requires yarn from the same suit which has aged in the same way as the sleeve that needs repairing. To do it you take out some of the yarn around the damage when weaving in the new yarn, weaving in the same pattern as the original weave.
In the past young girls were taught how to do it and there are beautiful sample pieces in museums, to find a trained girl (or woman or man) now will be very hard.
An easier repair, will only work if the damage is in an acceptable spot, is to place something over it that is very visible. Like the leather elbow pieces on traditional tweed jackets, or sweet flower embroideries on a female garment. So hide in plain view.