Your concerns are not unfounded. You absolutly need a fire wall. I wouldnt recommend a "fast" open conection without one.
I use ZoneAlarm on the software side and an SMC router on the hadware end. The full version of ZoneAlarm is about $25 and is down loadable from the internet. The SMC router with a wireless conection is just over $200. I set up my computer at home and hardwired it right to the router and my girlfriend (who sometimes works virtual) plugs into the same connection with the remote. Its a real nice set-up and easy to do. Oh yeah, we put a printer on the router as well so that she can print of her lap top.