1990 7.3 idi auto non turbo fly wheel removal a replacement

An automatic doesn't have a flywheel, it has a flex plate instead. The torque converter makes it act a lot like a flywheel, though.

But... you're probably talking about the flex plate or the ring gear around its edge. This is going to require removing the engine from the vehicle - there's no other possible way to get the flex plate out.

Once the engine is sitting on the shop floor, it's a simple job to replace the flex plate - first you unbolt the torque converter and set it aside, then you unbolt the flex plate from the crankshaft. Bolt the new flex plate onto the crankshaft, bolt the torque converter to the new flex plate, and put the engine back into the vehicle.