Outsourcing Intranet development. Interesting...
Microsoft developed SharePoint in an attempt to make creating Intranets "easy". SharePoint is anything but easy to work with. And it is expensive. But that's Microsoft for you. They take the "in for a penny, in for a pound" approach - hey you already use our other products (Office, Outlook, Windows Server, etc.), this integrates with what you already have!
A quick Google search for open source/free Intranet solutions turned up:
Developing a completely customized Intranet from the ground-up is possible too. But...
Keep in mind that the initial intention of an Intranet is typically "everyone will use it" and people are excited at first because it is new and interesting. So it seems like it will work wonderfully. But, in many cases, pretty much HR and managers end up using it and the rest of the employees loathe the site for one reason or another - usually because it ends up being static content and a pain to keep up-to-date with the general consensus that "e-mail is easier". Most Intranets die slow, painful deaths because SOME of the content is actually useful.
Typical things found in the average Intranet: Employee phone book, global calendar, forms (e.g. tax forms), announcements no one reads, and the daily lunch special in the cafeteria. Department-level areas restricted to certain people via LDAP/Active Directory might include login information to secure systems and specific procedures to follow that are at least six months to several years woefully out of date.
(There's a Dilbert cartoon or two in there somewhere just waiting to happen.)
(#6 just screams, "The Intranet died and someone was desperate...and bored!")
As to installing an Intranet, that should be done on-site or over VPN. Here's how I picture your scenario otherwise: You hand the files off to them and then...what? It'll be sent to someone in IT who is going to look at the files and ask, "What do we do with this mess?" There will be a long chain of e-mails and then everyone will throw up their hands in frustration and toss the problem back at you. Maybe.