pointing domains and backing up

My site is ccoceancity.com and we are having a new site designed for us and will, in the next few weeks, point our domains to the new site and different name servers.

My question is, if we only point our domain to a new server, what will happen to our existing WordPress site?

Will all the content be lost forever and disappear? or

Will it revert back to a mysite.wordpress.com address?

My issue is that I need to make sure this information on the wordpress site is available and accessible while we switch over to our new non-wordpress site.

I did not set up the site and therefore do not have a strong knowledge of how wordpress works and what the steps would be to back it up.

I have done an export to a new wordpress account and there is a good amount of info there but not everything.

Please advise, thanks
Jim