hottubenioyer

I'm 45 mins outside of Portland Oregon. My local service place where I bought it only can replace the unit itself

So about 1 year ago my 4 year old coast brand spa seemingly was dead for no reason. I called my dealer and he suggested I replaced the F6 30amp fuse viewable and the below photo. I replaced it and everything started working again for the next year everything was fine. Yesterday this happened (photo below) and now it's not working again. The model is a Balboa CST20X1 . My dealer suggest I'm going to need to replace the entire box for around $700. I'd like to know if just the PCB can be replaced and if so is this more complicated than replacing the whole control box or easier? Also I'm looking to get advice on preventing this from happening again. I am considering installing a surge protector before firing it up again to prevent this from happening again. Dealer suggested that it was from a surge, although I don't have any evidence of surge inside my house that were on any other appliances or sensitive equipment like our computers TV's etc. So long story short. Do I replace the PCB or the whole board? How did this happen? And will a surge protector help prevent this in the future? Spa is installed on a separate sub panel GFCI connected to the main breaker. Also if it is a surge, why didn't the controller have any built in protection or why didn't the fuse sacrifice. Thanks in advance