Alan has given you some good answers here, but I felt compelled to add to his message when I read
I am taking a 600 mi trip and wonder if I should take it in to the dealer, before I leave. I would hate to brake dowm on the interstate, as I am female
I think you should get it looked at before your trip. As Alan indicated, the problem shouldn't make it "unsafe"... but....
The stability control system integrates the variable effort steering and the abs systems, and adds a few other sensors to provide improved handling under adverse conditions. If the steering wheel position sensor is faulty, the driver may experience erratic power assist as well as the loss of the stability control system. This condition combined with poor weather conditions could make the vehicle unmanageable or unpredicatable.
Once a driver has "learned" the handling characteristics of the vehicle, the loss of the stability controls could result in "overconfidence"... what I'm trying to say is the vehicle will not handle in the manner they have grown accustomed to.
I agree with everything else Alan has told you.