Forms 1099-S are not always issued. Unless you know they are going to be sending one, you can enter the sale information from your documents.
If you need extra time and file an extension, it will waive failure-to-file penalties until October 18th. However, if you would have owed tax on April the 18th, the IRS will assess monthly late payment penalties and interest until you pay.
I recommend to extend your return with a TurboTax Extension and also pay your best guess of anything you may owe. If you overpay, it will be refunded. If you underpay, it will only calculate penalties on the part that was not paid.
TurboTax has a tool called TaxCaster to give you an idea of your tax liability and/or refund. You can vary different items and see how that could impact your return. Click for TaxCaster