Pluming company damaged my fiberglass shower pan trying to remove drain

[Nubia Silva]

I hire a pluming company replace a shower drain he quoted me at $560.00 

He had down the initial inspection and the never mentioned anything about the shower pan being damaged.

Today he came out and said that the that the drain was corroded from all the hard water and was not able to remove the drain, he them send me photos of the shower pan with a whole near the drain and the tools use to try to remove it. He them procede to tell me it had hair line crack and that possibly the water was leaking from there and that it was a wear and tear because those pans only last so long. 
(I have photos of the shower that my tenants had send me and there was no crack or holes) 

He is now quoting me $6k to change the pan or $9k to replace the entire pan and walls.

I told him I need time to speak to my partner (husband) we call him later and he said he would call us back but never did. 

Any suggestions would be very helpful on how to proceed.