1. When entering a system where "everything is a mess", it is an opportunity to redesign everything yourself based on what you have to work with and what the needs are.
2. You would be smart to immediately contact the ISP (probably your local telecom/phone company) that is providing the MAN/backbone services between the offices. Tell them you're the new guy on the block, find out what devices they are using, find out what the contracts provide in way of bandwidth, services, and support. If they can provide some utilization information, that would be great too. If you can develop a relationship with those guys, you will be off to a good start. Most network engys have multiple interests too, so they might be good sources for info on any issues you might run into. Depending on their ages, they may be into LAN gaming, be linux/unix nerds, or you could invite them out for drinks to develop some friendships. This could also lead to future employment (hint, hint).
3. Prepare yourself a testbed. This will require power (UPS & maybe generator), servers (3 or four), computer clients (junk PCs that work are fine) cables, switches (unmanaged layer 2 is fine, but Cisco layer 3 is "finer"
), and perhaps routers. You need to construct this test bed to test your design and see if everything works the way you expect it to (it won't, don't worry...which is why you get paid).
4. Outline ahead of time what services you need/want to provide and what you are going to use to do it. I would suggest that you use Linux for servers, since it is inexpensive, you can get online support from linux communities, and the server daemons get updated frequently. You'll probably be handling; DNS/bind, mail (Postfix, not sendmail please), security/firewall (look at the bastille-linux site, Jay Beale's firewall frontend is excellent), HTML/Apache, and some other stuff.
Basically, you have a huge task in front of you, and you are being very
underpaid. However, this opportunity will be a HUGE learning experience for you and will give you invaluable experience and a wide ranging skillset. Most likely, you will have a large amount of pressure (constantly hearing, "So-n-so used to do it this way, and we never had any problems..." and everything
will become your fault) and be overworked as well as on-call 24 hours a day. Lots of study, and working things out in your lab/testbed will get you to where you want to be. In the end, you will not even realize how much valuable experience you've gained, and you will be ready to jump into some big money (>$75K) within about 3-5 years with what you will learn. I've found that certificates don't mean nearly as much as experience to your potential employers, but they make a company look good (for bids on jobs or to your manager for his team evaluations), so don't worry about that too much. If you do need/want training or certificates, get the county to pay for it (just tell your boss that you need it). Local governments are very good about paying for such things, as long as it doesn't become abusive.
As long as you don't plan on having a social life and keep your nose to the grindstone, you will come out WAY ahead. This is just a stepping stone, but it sounds like an excellent opportunity.