Transferring newly built site from subdomain to active live website

Afternoon Ladies and Gents,

I did a quick search to see if my question has been previously answered, but couldn’t come up with a decent search phrase – so my apologies if this has been answered.

Our current website is http://www.floridagunexchange.com, and we wanted to redesign it and get it up to date. So, the subdomain new.floridagunexchange.com was created in order to design the new website, without the existing one going down.

Now that I’m ready to switch over, I’m trying to figure out the easiest way to do so. I didn’t want to just overwrite the wp-content folder as I want to keep existing plug-ins that we have (and I’m sure that’s not the best approach anyways). What is the best way to go about this? I want to keep the content from the current site, whilst adding all the new pages I’ve created in the subdomain.

Thanks ahead of time,
Adam