I think there are relatively few folks on this board who do merchandising. Friends who have undertaken it have found that just as with mystery shopping there are excellent companies to work with and really noxious ones. The merchandise is shipped either to your home or to the store (mostly to the store) and you will interact with store personnel to retrieve the materials from the storage room. Some store managers will be a delight, some will be a PITA. Some stores will be neat and clean and easy for you to do what you need to do, others will have stuff everywhere so you may even need to put away other merchandise in order to do your restocking. Some planograms are in good shape and some are inaccurate to the point of being impossible. Generally you will be working closely with a District Manager and that may expedite or completely hinder your work. Some will pay you by the hour and for mileage, some will pay you for the job regardless of how long it takes. Generally they pay on time and reports tend to be minimal.
Like anything else in life, a grab bag.