There are hundreds of species of ants in the US. My understanding is that there are few if any that will eat healthy wood. I believe it is rotten wood they eat. Now that may impact a tree in it's ability to heal - have no idea.
Here in NM, what I call a carpenter ant is a HUGE ant and are fairly easy to control with various baits. They are nocturnal so I've gone out at night and found their trails. Not like a typical ant trail in that it will be one ant every 2-3 yards instead of a steady stream. Anyway, I've personally had good luck with Maxforce products - both the granuals and the "gel" types.
While the products at the hardware stores can work - I have taken to using the same stuff the pro's use. Easily purchased on the internetIt is also perfectly legal....
For these ant bait type products the risk is very low - small amounts strategically placed. For some of the other products consumers can buy I worry a bit due to general availability. The labels need to be clearly read and understood as I suspect some of them are related to the decline in the bee population that has been going on lately.
Anyway, just google "do your own own pest control" and do a bit of reading - can save you a ton of cash. I paid around $40 for an ant control "kit" recently. Last time I did this, it lasted me for about 2 years. Compared to $40/visit from the pro's.
-Chak