Many shops can do it fairly quickly and will be willing to allow you to watch although there are sometimes design or detail issues about the job that add complications. Usually the biggest issue is one of scheduling. Most skilled setters are pretty busy people and they have other clients work in line ahead of you. There may also be an issue of security. In and about the shop are items that belong to other clients and they may be unwilling allow a stranger to be in the room at all, although many will provide a window into the shop area for this purpose.