There are two main ways to access South Coast Ridge Road.
The first is off 1 from Los Burros. I generally take that route. You're going uphill mostly, which is less intimidating.
The other way is off Nacimiento-Fergusson. At the very top, before you start heading down into Fort Hunter Liggett, it goes off to the right. To the left is Cone Peak Rd, which is gated (I'm not sure how far you can go before you hit the gate, though).
From 1 to N/F it's about 23 miles of dirt IIRC. There are off shoots that you can explore, the majority of which are dead ends. Those would add to the mileage.
Gas is available about a mile south of the entrance from hwy 1 in Gorda. It is most likely THE MOST EXPENSIVE gas in all of California, so top off in Carmel before heading south so you can avoid getting robbed in Gorda. Or at least limit the robbery to a light top off.