I assume you're setting up this network with Windows. It's pretty easy once you know what you're doing.
You have to configure your network cards (NIC's) so that they are all use the same IP Subnet. If you know where to find your TCP/IP settings in Windows for your network card, go there. You'll see a subnet mask that probably reads something like 255.255.0.0 - this is just like a mold if you were doing metal castings. Every IP address in your network should fit this profile. And you want to begin your IP address for your network cards with 192.168 because that is the subnet used for private networks. So you could use 192.168.1.0 for one machine and use 192.168.1.1for a different machine.
Once you get all of your IP address configured for each of your computers you have to make sure you put all of your computers in something called a Workgroup. You right click on My Computer, properties and there should be a button labeled Network ID if you're using Windows XP. You can set your workgroup name and the computers Network ID. You'll need to make sure each computer is in the same workgroup.
Once you've done all that then you just need to configure your firewall. Each one is different so look in the help file for network settings. I run ZoneAlarm. You can create a safe zone which can be an individual IP address, a range of IP addresses, or a subnet. I just did each one individually. Once your firewall is set to allow traffic from your networked computers you should be able to find your computers on network places. Once you've gotten this far, let us know. Then you can move on to mapping network drives which is fairly simple. One thing to know is if you're using the free Zone Alarm, it won't allow Internet Connection sharing. You have to purchase Zone Alarm Pro to be able to get internet on your other computers. Now, if you're using the router as a hardware firewall, you shouldn't have to worry about any problems if you use Zone Alarm because the router shares the connection, not your computer.
You were also interested in wired and wireless. Well obviously you have to have a wireless router, which you said your Linksys router is. So, you probably have to configure your router also to work with your network. Read the manual for that. From what I've heard you can set up your network one of two ways. You can run the internet, if you're using DSL or Cable into the router and then use a wireless card on your main computer and also one on your laptop. Or you should be able to run the DSL or Cable connection directly into your computer and also have a connection to your router. Then you just have a wireless card for your laptop. But the first way is the way I'm sure would work and probably the best way. The second way requires two NICs to be installed on your main computer.
So basically there's four things you have to configure in a Windows Peer-to-Peer network. You configure your network card, your firewall, your router or switch, and your computers. Switches are nice because most don't need configured like many routers do.
Edit: introducing the amazing "paragraphs" technology that can improve the readability of things up tp 100 times - Nodsu