Hi i did this trip before
it takes around 8 hours
roads are perfect.
It is safe.
you need to get pass visa from Saudi Arabia (you have to apply here before you leave) (150 QR/ passport).
UAE arrival visa depends on your profession here in qatar (check with UAE embassy)
on arrival visa 150 QR/passport
car insurance in Saudi Arabia & UAE depend on how long you will stay there (for 10 days 70 QR for each country)
i hope this will be useful for you
GOOD LUCK