Do you have the complete parts list for both photos by chance? That will help when ordering the parts.You're going to need the seal, and O-ring in second pic #20. Part no 21 has 2 different parts, get both. That's for locking the flange nut. If you're careful, you can reuse snap ring 23. Drain the oil before performing the job. I always recommend replacing the bolts and nuts at the flanges. They never tighten properly. Use care when separating the flanges, if you damage the slots, it will be very challenging to reassemble.
I could provide that later this evening