Hi Lydia,
getting prices for replacing teak depends on where you are. There's a good outfit in Nelson, and a couple in Marlborough, and heaps in Auckland.
We are in the same position of contemplating recaulking, refining,plug replacement and sanding versus new decks, but we are a bit bigger than you. For us, recaulking and sanding would be around $8-10k, plug replacement is on top of that. New decks are around $40-$50k for a 42 footer.