Have a reputable pool construction professional come out and look at it.
Ask him for his honest opinion of the condition of your pool.
I see these calls fairly often and have always told the buyers exactly what I'd do if it were mine. Some of the time it's fix what you've got. However, I've filled in plenty that didn't deserve the repair invoice price and I've demo'd some and constructed a new one inside the remaining hole. I've never bought into the build inside the old shell mindset but have done it many times for buyers who didn't want to pay demolition and haul off charges.

It shouldn't cost you a penny for a written estimate of how much it will cost to perform any of these job descriptions. If your man doesn't get back with you in a reasonable timeline don't give up on him. Give him a friendly reminder phone call that you'd really love to entertain his bid.
In my position on a pool like yours is that if the buyer isn't interested in a demo/hauloff and new construction price I always take my sweet time on quoting jobs like these because they're not my preferred jobs, I prefer new jobs and simple remodels. I always hope one of my competitors will pick up the job by responding quickly.
When I get the reminder call from them I apologize for the delinquency, write the bid, and I usually end up with the job. In my area there are a lot of builders but only a few are worthy of hiring to tackle projects like these.
We're truly blessed because we don't advertise and work seeks us because we're honest businessmen. Some builders will use a job like yours to write an open ended contract where they can get you for more than the actual value of the services performed on issues that may arise which were unaddressed in the agreement.

When picking a builder, before entering into a contract get phone numbers of some of his similar projects. Call them and ask them if you can come over for a quick visit and to see the pool. Do this in the builders absence so you can find out how the process truly was. If there were issues they'll always tell you stuff they wouldn't have if the builder was standing there. I've always done it like this. These folks have quite a bit in common and will converse for a long long time.

See ya,
Kelly

Thanks for the response.

My thought on building inside is that the pool looks huge to me (at least empty it does) and if I were starting from brand new I wouldn't make it so big and I would want it to be more unusual looking with a spa and/or waterfall.

Lisa