To protect your own interest this is the best advice given. I'm not sure of all of the laws in Mass. but here in New York my advice would be to get an updated survey FIRST. Just because you have two property corners dosen't mean there in the correct position, which is what a licensed surveyor would tell you, as well as be liable for. An updated survey would show any encroachments, if any, by your neighbor. After that that i would speak to a lawyer but he probably would suggest sending your neighbor a copy of the recent survey with the encroachments in a registered mail letter asking for him to remove the encrachments. That usually puts the person on notice and with the survey, proves that he's encroaching on your property. That most of the time settles these issues. There is much more to the actual survey end but this is why you hire a licensed surveyor. Call the surveyor on your old survey to get started, they most likely will be able to update the survey the cheapest and collaborate what i'm saying or point you off in a better direction. Good luck!....I speak with some knowledge, i'm am a land surveyor...