Letter from your company that they have no objection for you to take their car for umrah purposes.

1) the above for Here
2) The above for Saudi Arabian port authorities

Once you visa is ready, you take the letter and visa to the Trafic Police Department. they will give you "tasliyah" based on that.

Regarding car, I think thats the full procedure.

ask your agent if something else is required as well.