First off, I would recommend that you definitely get in touch with the initial inspector. Be firm, but don't give too much information away in your discussions with them. If they performed a proper fireplace and/or chimney inspection, they ought to have records, including notes and photographs or video from their inspection. If the inspector "approved' your home prior to sale, they are somewhat responsible if there are conditions other than as described. You paid for this inspection, and if indeed there are $3000+ in existing repairs needed, the initial inspector should be partly responsible. Don't be too forgiving, they should probably have errors and omissions insurance to cover costs such as these.
However, if they have evidence that there were not existing damage, then you may wish to get a third opinion from another sweep company from a CSIA accredited company. I would pursue getting to the bottom of the previous inspection and obtain any and all records possible prior to proceeding with any modifications. Personally I loathe how litigious our society has become, but this may be a case where you might consider seeking council once you have any records from the initial inspection.
Others have commented, open fireplaces are terribly inefficient as heating sources, and often will actually rob your home of heat rather than helping warm your home and reducing heating utility bills. Modern EPA II approved free standing wood stove, inserts and pellet stoves are all much more efficient means of heating with biomass.
If your chimney turns out needing such extensive repairs, it might be money better spent to have a good insulated stainless steel flue liner installed with a modern heating appliance. This will be a safer and more efficient means of heating your home, and would cost about the same amount.
Cheers, and keep us posted with what you find out.