This varies depending on the device. It depends on how easy it is to open. Basically, if you don't break anything during installation (i.e. the defect has nothing to do with it), it doesn't matter.
In the case of a warranty claim (e.g. a defective graphics card), you would most likely have to keep the old board and then reinstall it before sending in the unit (of course, there must be no damage from the installation). In fact, all manufacturers expect the unit to be in its original condition when it is returned.

So if you can just unscrew the screws and be done with it, it's no problem.

Some devices are glued together, which makes it more difficult and I personally would not fiddle around with them, unless you know exactly what you are doing.
But basically no problem: if you don't notice the change and/or the damage is not caused by a possible change.

Correct me if I'm wrong :)