in a week i am about to buy a 5 string. it has a laquered maple fretboard. i like the tone of maple, but i have heard that the nut on this particular bass is.......gasp....plastic. i was wondering which type of material, in a reasonable price range, would sound best.

that was question one, here's number two!

i would tune this thing EADGC, so is there a general fee for slotting(i have no idea if that's the right word) to do that? thank you for your time.

If you have never "cut" (or dare I say "busted") a nut, I'd take it to a shop/luthier to have them do it. Tell them what kind of material you want. I have found setting up a bass/guitar can be the most crucial part to make it play and sound right. If you are experienced in slotting a nut, then go for it. It's always nice to get familiar with.
As for material, I'd go with a bone nut. I haven't personally used hard wood like ebony/cocobolo/bloodwood, etc. yet but I definitely will soon. I'm curious what wood will sound like. I have guitars/basses with bone/brass/graphite/tusq that all sound really good, but different in there own ways. How would I know what YOU would like anyway???
Experiment.