New Computer for Video Production

Although I am computer illiterate... I manage to produce video stories for a living... simple and straightforward (oral histories on senior citizens in our area). Somehow I learn enough to get by and it works. I shoot with a mini DVcam and edit with Pinnacle on my 6 year old PC desktop computer. Which has just hit the wall. So I am shopping. I have gathered a list of specs from my "geeky" friends... but now need reassurance and to know the best place for me to buy this new system... pre-assembled (and I am on a budget).
I am trying to figure if I can even go with a laptop... or if I need to stay safe with a desktop no matter what (for unknown future needs). Any wisdom? Thank you in advance!

HD with RPM 7200 (some have told me I only need 5000)
Video/Graphics Card 256 MB
HD 160 GB
RAM 2 Gigs
USB Ports 4-6 ports
DVD Burner
16" Screen
Battery that lasts about 4 hours
Firewire
Wireless capability