Vets are now becoming much more used to seeing chickens, check with your local vet if they are happy to see poultry. As a first stop there are a huge amount of web forums to cater for the many new hen keepers (see my Links page) to help you with any problems your hens might have.
Ultimately a hen is a living creature and no less likely to feel pain or fear than a cat or dog, and if they are in any sort of pain would need to see a vet. By taking them on you are responsible for their health and well being, and before deciding to buy them, need to be aware that could include nursing them as well as vets bills.
They don’t need any routine vet trips (such as vaccination boosters).