This was a 1 Banana job as they say but I thought I would do a quick write up on how to replace the front seat belts.
1. Remove the front and rear door sill plates.
2. Remove the lower b pillar trim.
3. Remove 10mm bolt on top of the retractor and 14 mm bolt on the bottom of the retractor.
4. The trim on the shoulder bracket can be tricky if you don't know how to unclip so I drew up a little diagram with pics. Pinch the adjusting buttons together and insert a trim tool to unclip the bottom of the cover. Then pivot the bottom cover outward. See pics.
Reinstall in reverse order.