Have just got a cat from cat protection 12.5 years old indoor cat .. Supposed to be very timid ..Poor cat pop and weed on way home so ran out of cage on opening .. Found a corner for 10 minutes .. found food ate it and explored ..came out for cuddle and climbing everywhere .. when I left room.climbed onto sofa .. Question how soon can I start trying to swap her to different food and cat litter aware to mix together first