P0720 intermittent

Good day house. 

I have a Skoda fabia 2007/2008 model. I've been having issues with the gear engaging on time. I will have to leave it to run for a while and before engaging the gear and when on the road, it delays in changing to the next gear and when I accelerate the more I hear a sound like(hooooo) and I will have to release my leg from the accelerator then it picks and the same happens to the next level. 

I scanned the car and I got a code: P0720( output speed sensor circuit). 

I was told the output speed sensors is in the gear.

I was also adviced to change the whole gear system.

I sincerely need a help. What should i do? The car still moves but not the way it should.  

Awaiting any useful information.

Thank you!