Hello Marc,
This service is not offered by digitec. Depending on the case, you would also have to be careful when installing it yourself. Sometimes such fixed PCs are also sealed, in which case the manufacturer's warranty "COULD" expire as soon as the case is opened. A service centre may be able to offer this service (e.g. http://www.littlebit.ch/), so that it is then sealed cleanly again.
Greets