Go over your service records to see what has been done previously. Look in your owner's manual to see what is recommended but I would start off with changing all the fluids, engine oil, transmission oil, brake fluid if it has not been flushed withing the last two years, have an inspection done of the brakes steering suspension, tires hoses and belts. Tell the repair shop you choose that you are taking a long trip. Get the service done soon don't wait until the last moment just in case anything more serious is noticed.