Security for network with WAP

This is probably a really newbie question, but...
I have a small office network with an 8-port wired Linksys router. Our office computers, and 2 network printers are on it.
In order to give our guests wireless access, I purchased a Linksys WAP, which I connected to the wired router. Setup was easy -- so far, so good.
The security on the wired side is where I need help.
We have file sharing on the office computers, we have network discovery turned on, etc. Between our computers, we share a lot of files and folders. I'M not about to try to password protect files on each of these computers. And since I'm behind a router, I do not use firewall software on these machines. (I check security with Home of Gibson Research Corporation and always get a 100% stealth rating)
So... How do I set up the WAP so guests can get to the internet, but make the "wired side" of my network invisible without a bunch of grief?

If you're using private dial-up server and a private WAP gateway, you're getting the best security. You can switch on logging of RRAS server. This is described in Microsoft KB record Q161426. Then all of data sent throught RRAS, including password if sent unencrypted, may be logged into WinNT/Tracing/ directory.

yes its a nice solution