I travelled twice last year. No need of No Objection letter. Car must be registered on your name. Only family members can travel together.(I think).

There is a place on the road left from Sana round couple of buildings after the Merc Showroom where you can apply for the Saudi Visa. These are the agents. Visa takes 1 week and cost about 75 including the commission. You have to give two photgraphs , your passports, Letter from your company stating No objection to travel (English is OK) and copy of your car registration.

UAE visa - you can get at the border if you are a Manager or Engineer or one of those exempt categories, in your Qatari Visa. Thats about 103 per head.

Make sure you traffic fines are all paid.

As you cross the UAe border make sure you are refuelled as you may not find any pumps on the highway.

Its 700+ Km Doha to Dubai. Pretty much empty most of the way.

Once you reach Dubai Make sure you buy the Card for the toll crossings just after you cross into Jebel ALi.