I second the motion!
Have a great trip, and as the others and more savvy folks here have told you ... forget about driving. It is deceiving.
While we refer to it as "driving" in the RD, and it ocasionally looks like driving as you know it, in reality, it is more like navigating a HUM-V through enemy fire and land mines, after five shots of strong expresso and no sleep.
Now, are you still interested?
I am no granny driver. I HAVE driven in Italy, and Moscow, and around lake Como, and in the alps, and the entire coast of Spain and France.
That said, I would never recommend "driving in the RD" to anyone visiting the RD for their first hundered times. Especially if you do not speak Spanish fluently and do not look like a local.
Save your adrenaline for activities with a bigger payoff!
Among other unexpected surprises, try this one on ... imagine a local hitting your vehicle, and you pay for their damage! It is too crazy.
The upside of paying someone to do the driving is that YOU can enjoy the FANTASTIC scenery. Please do just that and make sure your first impressions and memories of the RD are all positive ones.