Connecting a Mac to a windows network

Hey guys,
I am soon going to be replacing my Windows PC and Laptop with a mac pro and Macbook/pro and as I can't currently afford a 2nd mac to use as a server, I'm thinking about the possibility of using one of my Windows PC's as a server.

However, I have a couple of questions
1) Is it possible to log in to a windows domain on a mac? (for drive sharing, etc).
2) Is it possible to do the above using WiFi or can it only be done (if at all) through ethernet?
3) Would I be better off just using a NAS/Saving for a G4 tower to use instead?

Thanks