My understanding is that you was not a formal beneficiary of the property - but your Uncle was - that is important because if you owned share in the property - you would need to report the sale transaction and might owe capital gain taxes.
So - my understanding is that your uncle inherited the property, sold it and decided to share with you part of proceeds to fulfill the wishes of your grandfather.
If my understanding is correct - the transaction is classified as a gift (you are not obligated to pay that amount back) - as a recipient of the gift - you will not include the gift into your taxable income.
There is no any amount limit. Please see for reference IRS publication 525 page 33 - http://www.irs.gov/pub/irs-pdf/p525.pdf
Assuming Uncle is not an US citizen and not a permanent resident of the US and the gift is from abroad - your Uncle does not need to file a gift tax return and will not owe any gift taxes.
In case you transfer the money to US - if the amount is more than $100,000, you are required to file form 3120 - http://www.irs.gov/pub/irs-pdf/f3520.pdf (see instructions for details - http://www.irs.gov/pub/irs-pdf/i3520.pdf) to declare transfer from the foreign country. There is no tax associated with this form.
Please let me know if any clarification is needed.
Tax Preparer
Taxes, Immigration, Labor Relations