Speak with a real estate attorney before agreeing to anything! Changing your deed changes what you own--it could be good in some ways (possibly adjusting taxes) but bad in many obvious ones (e..g you find you own less land than you thought you did). You do NOT have to take your neighbor's assertion that your land survey is incorrect at face value, and you do NOT have to make any change to your deed unless (1) they sue you and (2) prove their case. Speak with a real estate attorney to see what the possible ramifications are and how best you should respond to preserve your rights and economic or  financial interests. Good luck.