Before you attempt any repairs or maintenance on a Frigidaire washing machine, you should always unplug the appliance first. Move the washer far enough away from the wall so you can unplug it, and give yourself plenty of room to work both behind and in front of the washer. Once the unit is unplugged, you can move it around as you please to gain access to all the spots you need to reach. It is also important to watch out for sharp edges when you have your hands inside the washer.
Frigidaire washing machines have screws in the back that secure the top panel to the rest of the machine. Once you are behind the washer, you can simply remove those screws and lift the top panel off. That gives you easier access to the main tub and the seal you need to replace.
After you have full access to the top of the washing machine, you can clearly see the motor and the drive belt. To get started, remove the drive belt then unplug the motor while leaving the wiring in place at the bottom of the washing machine. Unscrew the screws that hold the motor in place, then carefully lift it out of the washer. Then go to the right side of the washer and remove the rubber drain trap from the tub, along with the water level sensor. Removing these pieces makes it easier to find and remove the main tub seal.
You must remove the shocks to gain access to the tub seal. Simply push the lock tab and slide the pin out to free the shock. Place one or two blocks of wood under the tub to support it in the absence of the shocks. Then carefully cut the glued places where the existing seal is glued in place, then remove the clip that holds the fill spout in place. At this point the drum will be hanging from two large springs. Remove the clips that hold those springs in place, then disconnect the drum from the washer frame. Remove the springs so that the tub is just resting on its supports.
Carefully lift the drum out of the Frigidaire washer. Lay the drum on a blanket or other soft surface, then remove the screws that secure the two halves together. Lift the top half off, then carefully remove the tub gasket seal and replace it with a new one. You can remove the old seal by gently prying it up with a flathead screwdriver.