Yes, indeed there is a front and rear of the disk, so pay attention and put it in the right direction.

On the 124, you have quite a bit more to mess with, however. Assuming this is a US car, you will need to lower the exhaust system out of the way. You will unbolt from the manifolds and remove other hangers to lower it. You will have to remove the front passenger floor mat and disconnect the O2Sensor and feed the cable through the floorboard hole.

You then will loosen the large nut in the front driveshaft section to collapse the drive shaft. Is this does not gain enough room, lower the center carrier bearing. Before doing this mark the position of front and rear shafts so that they can be put back in correct orientation if they pull apart accidentally in the process. It is possible that you still won't have enough room to work and will have to pull the rear flexdisc down. The rear one is not subject to near as much heat as the front so it will be in good shape.

Good luck,