I have a similar set up to your discription. What I have done was connect my printer to a print server (Linksys PPS1UW) that is connected to the router. This allows me to keep only the printer on all the time without the need for having the computer it was connected to on, also. What this allows is for the printer to be shared on the network and not through a PC. In my case I have 2 desktops connected to the router via cable and a wireless desktop on another floor. All which can share the printer. You need to make sure that when you install your printer that you choose the correct port assignment. It is not your LPT1 port. Hope this may give you a additional option to try.
As for your sharing issue, you can right click on any folder that you want to share with other computers and follow the directions to enable sharing.