I had to remove the oven from my 86 Sov last week. I hope the process is much the same. Here goes:
SWITCH OFF THE GAS!
Looking at the oven you will notice that the sides of the oven sit proud of the counter top. On the inside edge of that raised trim you will see screw heads, on mine there were two on either side. Having removed them you will feel a little movement in the oven, but don't pull too hard because the gas pipe is still connected.
Remove the pan supports. Lift the stainless steel section of the stove top - Its hinged at the back. You should see the gas pipe running from the back of the unit to the front under the RH gas burners.
You will need two spanners: one to fit the supply head and another to lock the fitting on the oven fitting. If you don't lock this it will turn and the gas pipe will begin to twist.
Having undone the gas pipe, pull the whole unit out bodily. The supply cables have enough length to allow you to take the oven out. Dont twist the unit as it comes out, the gas pipe needs to be fed through the access hole at the back of the oven.
I find it useful to have a box for the oven to sit on - placed in front of the sink cupboard - this saves your back and ensures that no grubby oily stuff which might be on the oven gets on the floor.
Good luck AND DON'T FORGET TO SWITCH THE GAS OFF!
Coming soon: How to convert your twin to a double bed!