The noise from the tensioner has increased over the last 6 months. There also seems to be quite a bit of vibration from this part when the engine is running. Does it need to be replaced and how easy is it to replace?

Pully might be worn, which can make it wobble.
Its easy enough to replace blindfolded with your feet.

remember that the bolt on the tensioner pulley is probably a left handed thread.

Remember, you can buy just the pulley and bearing at the parts store. Don't buy the whole arm assembly, unless the spring feels weak.