It's not very hard to do the wiring as long as you have:
3-way switches (they have 3 screw terminals vs. 2 on a regular switch).
A 3-conductor cable between the switches (3 insulated wires plus a ground for 4 wires total)
There also needs to be wiring from each switch to the light fixture, which it sounds like is already there.
Do a search for 3-way switch wiring and you'll find plenty of wiring diagrams. Make sure the power is off at the circuit breaker before you mess with anything. Use an electrical tester or VOM in both boxes just to be sure. If the switches aren't working right, they could be fed from different circuits.
If this doesn't make sense or intimidates you, get an electrician. You don't want to risk starting a fire or electrocuting yourself for the sake of a couple of hundred bucks.
