"To calculate my Capital Gains, do I simply subtract that amount from the selling price of the home?"
Yes, your capital gain is the selling price minus your basis. You also subtract selling expenses, such as a broker's fee.
In TurboTax you do not enter the capital gain amount. You enter the selling price, basis, and selling expenses. TurboTax will calculate the gain.
The capital gain from selling inherited property is always treated as long-term, no matter how long you or your parents actually owned the home. In your case it doesn't matter because you and your sisters owned the home for more than a year anyway.
"I have the appraisal done by the realtor that sold the home, back-dated to my father's date of death, to use as the Cost Basis."
A realtor is not a licensed appraiser. The value stated by the realtor is essentially an educated guess, not an appraisal.
"The realtor says he did not do a current appraisal on the home as the buyer paid cash."
I'm not sure what the realtor's point is. What the realtor might be saying is that a current appraisal wasn't needed for the sale because the buyer did not get a mortgage. If the buyer had gotten a mortgage, the lender would not have issued a mortgage without a current appraisal. But that has nothing to do with you. The current value of the home does not affect your capital gain or your tax.
