form or usercontrol ???

Question

Hi, i am new in c# an i want to write a little program. My pgm should have a mainform with buttons that open a stockmanagement(3 forms/windows)  and a suppliermanagement(3 forms/windows). How can make this ? Each window as a form or the mainform as a form and the modules(stock/supplier) as usercontrols or the mainform as a form and the modules(stock/supplier) as panels ?? I learned the basics from books and the samples and exercises were very simple (max 2 windows/forms). Can somebody give me links to tuts or samples about my problem. (sorry for my english, i am from germany and not so fit ) by jogi