Ok so I'm new to domain mapping and want to ask a few

Ok so I'm new to domain mapping and want to ask a few questions beforehand to prevent prolonged downtime.

I currently have 3 sites with domains like this: mydomain.com/usersdomain/

I want to move /userdomain/ to there own URl. If I'm understanding correctly the plugin "Domain Mapping" can achieve this with no issues(?).

Since the sites are already made will I have to fix broken links after the move? Anything I need to worry about?