Just make couple of non-camping road trips. Pack a lunch and spend the day driving to an area you are considering, since you are only talking a couple hours, and scope it out. Take a note pad, so when you get the campground you can make notes about sites you may like or want to stay away from. I too live near the Sierras (central Sierras), and we have made lots of day trips scouting sites around Shaver Lake, Huntington Lake, Bass Lake, etc. We are bit long for remote forest service CG, so the roads aren't much of an issue, but getting around some the CG loops are. As tent campers we went to some amazing remote campgrounds that no RV should ever attempt --- not being able to get there maybe the only down side to I have found to becoming trailer campers.
The problem with maps is they are outdated as soon as the are published. If you are talking about forest service roads, they change every year with trees falling, rock slides and pot holes...I just prefer to trust my own experience more than a map. Heck in my everyday driving the GPS often picks some very convoluted routes vs what I would have picked.
2007 Chevy Duramax LMM/Allison
2012 Jay Flight 29QBH
2012 Jay Flight 26BH (Sold)