Regarding removal of the window motor, it's not that you can't find the screws. There are no screws. The window motor/regulator module is riveted onto the door panel. To remove it you must grind off the rivets. When installing the new module, the rivet holes must be bored out and over sized nuts and bolts used to secure the module. Yet another good reason to be sure that it's the motor before replacing it.
Even though your car is a 1999 model, it is the old body style (e36). The manual that you need is the 1992-1998 3 series repair manual. I suggest buying a Bentley manual instead of Haynes, but they cost more.