Just come down. We had travelled last year when I used to stay in Saudi. You need to have the Iqama with the exit / re-entry visa. Have a credit card to make the payment at the border. Carry your passport of course (with sufficient pages available and validity) and have all the papers cleared for the car like the istimara, insurance etc. I dont remember the exact amount I paid at the border for the visa issuance and the insurance. That I think you can check in the govt websites. Ensure that if your car is rented / company provided you need to have the necessary NOC issued by the original owner and I guess you need to have that attested at the muroor. I cant confirm that since we had come in our own car.