I beleive you mean V-Brakes http://www.bikepedia.com/quickbike/B...foot&Type=bike
At any rate. The cost to make such a change:
Brakes - $80 - $150
Wheels - $150 - $350
Cables - $15 - $25
Fork if needed $150 - $350

So even if your bike was disc brake compatible, this is at least a $250 - $300 decision without any labor assuming you ar capable. An 11 year old $500 bike makes this swap a poor choice from a value standpoint at best.