week 1:
give red turnip to wendell for country guitar. give guitar to K.K. slider for his pic.
week 2:
give red turnip to wendell for turban. give turban to saharah for red vase. give red vase to redd. give the safe to tom nook for his pic.
week 3:
give red turnip to wendell for another turban. give the turban to saharah for a massage chair. give the massage chair to tortimer for a scallop. give the scallop to pascal for the golden axe.
week 4:
give red turnip to wendell for yet another turban. give the turban to saharah for another massage chair. give the massage chair to tortimer for the scallop. give it to pascal for his pic.

even though you are done with the red turnip trade quest,i'm pretty sure you can still repeat some steps to get the items again,or you can just order them off the catalog. Also, I know I refer to these steps as week numbers, but you may not get what you need every week.