If you can currently print to the printer from one of the machines, you can just share that from there and not need anything else for that. If the printer has a network card in it (the model number has an N in it usually if it came with one) that's even better.

You need at a minimum a cable/DSL router. After rebates, you can get them for anywhere form like $10 to $60 for the older models, or more for the newer faster ones. I have the older one, and it's totally fine. Get one with some wired ports, then you can plug the 4500 and possibly the printer directly into it.

There are stand alone network storage devices you can use or you can just put a 200 GB drive in the PC and share it from there. Both have advantages and disadvantages.

Setting it all up is insanly easy now, it pretty much does it all for you. It's pretty much plug and play now.