new grip

Had a lesson yesterday as my power slice had started to come back. We changed my grip leaving my left hand the same but moving me right hand thumb further left this feals a little uncomfortable mainly i think cos im not used to it. how long should it take to get  comfy with this. I also got told to feel like im hitting the ball to 1 aclock and extending which made me have a little draw did this for a while and managed to group my balls close together.
then when i went to play last night everything went wrong hitting fat shots thin shot everything when i did hit right they whent like on the practice range.