First, I'm sorry to hear of your troubles Jen. It sounds like you did your due diligence when you purchased by seeking the assistance of a home inspector and who ever caught the fact that there was no CO on the addition was doing a good job.
I agree that it sounds like the foot valve needs to be replaced. The quote of $5,000 sounds outrageous. I've had very good luck with Dalmik Well Drilling (they service Eastern CT) and if you call them at (800) 922-6220 (Linda or Mike) you can confirm if the original quote was reasonable or not.
Home maintenance items are recurring and something that needs to be expected. I regularly post about homeowner maintenance on my blog ( http://www.gardenrealty.com/MyBlog ) and there's some good info there for you. Unfortunately, most older homes don't have warranties like new homes, so the cost for repairs will likely be yours.
I hope this info helps and best of luck since home ownership should provide you with a more positive experience and pride in ownership.
Greg Hanner, Broker, REALTOR, e-PRO
It sounds like you mean it is priced over the tax est. value. Yes is could not appraise, but it could be renegotiated after the appraisal. Some towns are low, others are over priced. Get a good Realtor to help you price a good bid.... more