Skoda Octavia || Exhaust system light

Hi guys

Long story short, my exhaust system light came on about a month back, garage ran a test and said the front O2 sensor needed replacing. I brought a new one, installed it whilst the car battery was disconnected for approx 2hrs, and since reconnecting the battery the Exhaust system light is still there....is there any way I can reset this myself or must I take the car back to the garage? One last thing my electric windows don't work line they used to, now I need to keep the button held down continuously to open and close the windows where as before I cod just click it up or down once.... Thanks guys