Yes to the PPP question, just remember to point the PPP to your Modem.
You should be able to go to Chosser and select Appleshare to see your LAN, if this what you had before.
If not the network all depends on the OS's running.
Win NT/2000 Server's install services for Macintosh, then setup shares.
Win 95,98,NT,2000,ME and XP desktop, you need to install third party software. Either DAVE or PMAC Lan. If you can't fix it in 20 minutes call someone who can.