Switching Changing Domains for MultiSite

I did something a little... unfortunate.

I'm building a site for a client and I have all the site ready to go (well ready for them to go and fix the content). The problem is that I need to make this into a MultiSite install with multiple domains.

Ok well there's a plugin for that and tons of instructions.

However, i don't want to use the domain of the first site as the base domain for the network. We're going to be using the domain with a TON of subdomains (its the marketing site for a SaaS) and I'd rather keep things clean. Since the network is going to be all for the company, I'd rather have "Network.OurBetaDomain.com" as the root domain.

I tried installing the network using the original domain (with subdirs), creating a new site for the network site, then changing the siteurl and home options to the "right" domain, and then editing the configs to use the right domain and the new value for BLOG_ID_CURRENT_SITE and it all seemed to work.

However, when I went to enable domain mapping, I couldn't get it to work because the AJAX was trying to reach my original domain, but I was on the new domain (CORS failure).

I've since disabled multisite and I'll run multiple installs if I have to.

Is my best bet to take the database backup I have (W00t! I remembered to do that for once) and do a search/replace of the old domain for the new domain, replace the existing data in the database, and then setup multisite and domain mapping, and finally recreate this first marketing site by using the copy cloner?