b) No. Never tell a car salesman what you're willing to pay for a car. That becomes the starting point from which he'll only go up. In your case, the reverse. I'd hire an independent auditor to valuate your business, giving you a high, low and median selling point from where you can intelligently negotiate.
Your diligence needs to be done as to whether or not they're actually a good fit to buy (qualified?) and research them to see if it looks like they may be interested in your company from more than just a buying perspective, because they could just be shopping you and there's no need to disclose everything.