Your machine is in a wooden box/base rather than a cabinet, right?
If so, then there is probably only one little "nut" that swings over the edge of the front right side of the bed. Swing that out of the way and the machine will tip backwards when you hold down the front of the wooden base/box.
If there isn't anyone around to help you, you can swing the nut out of the way and when you lift the machine, the base will fall away on the front edge. Lay the machine on its back on the edge of the table and you can oil and clean the underside and loosen the feed dog.
You should not have to touch the rear hinges or the screws in them at all in order to get access to the underside of the machine.