Here's the deal op. At some point maintenance on the gutters was stopped. cleaning the gutters while making sure they are secure should be done at least yearly. During that time the gutters got filled with junk and was not able to drain properly. Add in a good rain and that detaches the guttering and water gets to where it is not supposed to, and thus the problem you have.

The only real way to know is to take out a small section of your soffit that's damaged and see how far back the damage goes. If it's only the fascia that's damaged I would suggest that you save your self some time, money and effort, and do it your self. On the other hand, if the damage goes back further get a contractor out there.

Edit: make sure to check the boards that are touching the fascia.