Torque Convertor

I have a class A RV. Ford chasis. It has a shimmer or vibration between about 26 to 31 mph, when applying the gas, not while coasting. I have been told it probably is the torque convertor. If you think the same thing, how expensive is it to repair? If I drive on it for a little while longer can it cause damage to something else, could I be stuck out in the middle of no where, or will it just continue to be an annoyance? Thanks.