Remote won't turn tv off or on. Mute, volume also does not work

The other night the remote wouldn't change the volume, turn the TV off or on, mute doesn't work but remote operates the Direct Tv box ok. Changed batteries tried reprogramming. Sometimes it works for a minute or 2 then quits again. Ordered a brand new remote matches the TV and the same thing happens with the new remote. I'm thinking its the photo eye in the TV or something and not the remote. How hard would it be to change the part in the TV?