It's a harder job to do then you are thinking it will be. You need to cut out the concrete apron then the stairs are all concreted in underground. Then you are about to find that the stairs might not match up perfectly. 8' stairs are not alway 8' exactly. They could be off by a couple of inches. You won't be able to save the liner. You will never be able to line the stair strips back up with the original holes. Good luck on this venture. I'm guessing you got such high quotes because this job is more difficult then putting in a new pool. What's the exchange rate from Canadian to us? Those steps I would sell for about 2k. Add a liner, fixing deck and labor and you are talking a 15k job in the us so the prices you got aren't unrealistic depending on exchange rate. Are your stairs thermoplastic or fiberglass?