Child Theme Update – Best Method

I am looking to use the new Theme: – I am happy to start the entire set up process again [from scratch] except –

I have a lot of content which I need to reconnect to.

Should I..:

1 – Delete the both the main [existing] classifieds theme and the child theme
2 – add the latest classifieds theme
3 – add the new child [car dealer] theme
4 – set up objects etc

Will my existing pages remain? Will my content be accessible? I have a CSV import set up with an important client – will this be disrupted in anyway – in this procedure?

thanks for anyone’s help on this – esp after looking at a wide range of answers on the forum.

cheers