Can I share or import data from another Drupal site to my current site and then export back?

Hi all,
I would like to know whether it is possible to import customer profiles from an external MYSQL database (ie, from another drupal site hosted on a different server) to my current drupal site to be used for running my applications and then export them back with some profile modifications?

I would like to keep the main database site separate from my application site and run it with only necessary data fetched from the main database. Will this system work? Is it something complicated to administer?

Is there any other way of doing it? I think ,using a sub domain to host my application site might solve this issue ... But practically I prefer to have two separate sites in different servers to keep atleast one site unaffected by any possible server problems.

Can someone answer me? I am not a technical guy....

Thanks.
Binu