My Haynes manual only mentions 4 mounts. One on the pulley end of the motor, one at the rear of the engine/transmission, one on the front of the engine and one on the tranny. If you have a good look around you'll find them but you might need to get underneath to see them.
Look for black liquid leaking from them or torn rubber. Check also that the bracket bolts haven't worked themselves loose
No idea on replacement costs. A good one from the junkyard might be a better cheaper option. You'd be very unlucky if you had to replace all three.
Labour is not much compared to some things but if your handy you could do it yourself.
It really isn't an urgent problem though so take your time.