[Decolliber]

We have only one computer at home connected to the internet via a DSL modem. I use Zonelab-Pro as a firewall and Symantec anti-virus (corporate editon), both kept up to date. My ISP is telling subscribers that they should also use a router as another line of defense against hackers, even if you do not want a home network. I would prefer not to have another piece of hardware - more things to go wrong and drive me crazy.
So here are my questions:
1. Do I really need a router or are Zonelabs + Symantec sufficient protection?
2. If I do get a router I would want one with a wired connection to the main computer and a wireless connection to another (future) computer elsewhere in the house. There is a bewildering array of routers with different specifications and I have no idea what to consider. Any suggestions?
3. Will a router slow down the speed of my internet connection?
4. Is there a good web site that will explain "everything you ever wanted to know about routers" or "routers for dummies"?