L.S.
I would recommend Dallas Gutter & Repair. I had the same problem with my gutters (in Carrollton), and had several companies come out to give me estimates. Every one (except for Dallas Gutter) told me that I needed to replace all my gutters, and one company even took down the gutters that were hanging and took it with them - now I have no choice but to replace the gutters! Dallas Gutter was the only one who gave me an estimate to repair the ones that could be repaired and replace the ones that couldn't be repaired. They also gave me a list of about 100 references. They are members of the BBB also.
Good luck!