Well, it seems things don't look so bad with the tank. Unusually, it was the right side that developed the holes. They were a small series of holes that spanned from the bottom center outwards
I misunderstood the comments about the tank sealant, and it appears it will last for an indefinite period of time, and it was subsequent rust development the shop guy was concerned with. I think that applying the sealant on the outside and then using Kreem on the inside may take care of business.
I'll probably keep and eye out for another tank anyway, but the heat's off for now.