The spray arm and support are a one piece deal like many of the GE built dishwashers are.
Spray arm parts link
To Remove Lower Arm and Fine Filter Assembly:
1. Remove lower rack from dishwasher.
2. Gently lift and rotate lower spray arm counter clockwise to remove.
3. Rotate nut hub counterclockwise to remove. Gently lift fine filter assembly up. Remove fine filter drain from sump.
4. Clean fine filter screen if soil is present.
5. To reinstall fine filter and lower spray arm reverse procedure. NOTE: When installing fine filter make sure the drain port of the filter is engaged with the drain for the fine filter.