I've brokered deals that large and can tell you it will end up being more complicated than simply using Escrow.com...especially if you end up with a deal where multiple payments are involved. Even if it's something simple like a payment structure of 50% down, and 50% due by a certain date.
Typically the buyer will be using a lawyer and will have some documents put together to ensure everything goes as planned. Knowing this, it is definitely prudent for you to be equipped with a lawyer who is very familiar with contract language and asset sales to make sure you are protected as well.
It's also a good idea to have your own contract prepared as it's never in your best interest to have the other party holding the position of power when it comes to the fine details of the agreement.
Some of the documents/contracts you should expect to see are...
Non-Disclosure/Confidentiallity
Asset Ownership Transfer
Sometimes you may even be asked to sign a Non-Compete depending on the type of deal.
Hope that helps.
Cheers,
-Midgetlov