Yes it will or could. It is what is called a material fact and must be disclosed under the law. Once disclosed it is going to affect an offer and thus the price. Get it remediated and it will be much better for the sale.
Yes it will. Best to get the situation solved prior to selling if it is at all possible. Expect the solution to cost upwards of $1100-some as high as $3000. Your number is not that high-I would recommend another test before I lay out the cash for remediation. Another solution is to disclose the radon level to a potential buyer along with the estimate to fix the problem and reduce the price of your contract by that amount or have the closing folks write out a check at the closing table for that cost (thereby reducing your net amount after expenses)