We have a multisite setup and its been setup internally,

We have a multisite setup and its been setup internally, with the url

http://server.company.co.uk/project/

Now we need to get some testing feeedback and to make it available externally outside our firewall it needs an 'external' url
http://project-dev.company.co.uk

Ive had a look at how to change things, but it seems a lot more involved than a normal site. I presume I have to search/replace in the DB for the url and also change the htaccess file.

But will this change it for the whole multisite setup? Im wondering if this is going to cause bigger problems.

thanks