Not all yanmars are redone in Vietnam, but the ones that are done there are where the horror stories come from. As far as I know, there is no easy way to tell where it came from. Just check the tractor out very, very, very carefully.
Parts are getting eaiser to find everyday. The people at
Hoye tractor are great to work with, and have interactive parts menu, that allow you to click on the part of the tractor, then find the picture of the part you need. Makes it easy to get the right part without knowing the right name.
My little 1500D has been a workhorse for not alot of money; allowing me to get a tractor that is 4x4 without breaking the bank. That being said though... Despite any reworking that was given these tractors, the are still old machines that spent the the first half of their lives sitting in a rice patty. You must be comfortable with working on them yourself, or have a good friend that is, since you will not have the dealer support that other tractor owners have.
Also, they do not have seat belts, ROPS, neutral safety switches, or just about any other safety equipment that newer tractors have. These little machines will kill you if you are not careful, or do not pay attention. To begin with, most of them are narrow machines that do not like slopes at all. They like to roll over on them, and you will not have any protection if it does. I have run construction equipment and larger farm equipment on slopes steeper than 1:1, but I will not take my 1500D on hardly any slope.
They also will start in gear and will stay running and will run over you... or your livestock or your kids. Be careful.
As long as you know what you are getting into, they can be great little machines that will save you lots of work. Also you might read up at
Tractorbynet. There are alot of yuppies on that site that buy what would be dream tractors for us, just to mow their yards, but there is tons of good info on alot of tractors as well.