More info about which Graphics card and which motherboard would make the advice given more relevant.
There are too many types of both for me to comment atm.
I have a Geforce2 mx/mmx400 (32MB) on my Work PC running Windows 98SE and that was enough for Morrowind, so inpriciple, your friend is right, 32MB should be enough for NWN.
If you have a broken/old Graphics cards, or your MoBo only supports AGPx1 or x2 then is moy not be enough.
More info please.
Too much is never enough in these circumstances.