reidisaki

What are my options for repairing this and how much would it cost estimated. its about 6' x 6' 4 seats and 4' deep about. I was wondering if its better to rip all of it out and put in some gunite and pebbletec or is it worthwhile saving this fiberglass and just put in new grout. How long would regrouting last? the fact that I can touch the grout and it turns into powder is concerning. Thank you in advance!!!!