When it comes to just setting up a TCP/IP connection for the purpose of accessing the internet, you should have no problems once you get a network card for what ever Amiga model you own. You'll need a TCP-IP stack for this, something Miami would do.
Also, I recommend using a hardware router that connects directly to the internet. Makes things easier I think. I use the Lynksys 4 port router and haven't had any problems with it. The router also adds a decent NAT firewall which will make your LAN stealth to the outside world, unless you decide to open up some ports.
If you want to setup file sharing between Amiga and PC, that too is possible and I have done it between my A4000 and WinXP box. It works quite well actually, I can browse my Amiga directories on WinXP just like any other network drive. To do it, you'll need to get a hold of Samba for the Amiga, which is freeware. There should be instructions included with Samba, so you might wanna get that now and take a look to see what's required in the setup (can't remember off hand).
If you want to do printer sharing, well, I can't help you there... If I remember correctly, printer sharing wasn't implemented (or was buggy) in the Amiga version of samba. It's possible it has been fixed.
Good luck!
- Mike