It's a beautiful drive, but some of the sections will be a little tight with your motorhome... especially about 10 miles north of San Simeon.
You can take 101 south to the CA-46, cut west over to Cambria, then head north to San Simeon. Plenty of places in that area to access the ocean.
Then again, I'd just make sure the brakes and suspension are in good shape, take PCH at a gentle speed, and enjoy the scenery.
Top off with fuel/water/food before leaving the Monterey/Carmel area. IIRC, the few stations along that drive will be rather expensive for everything.
There used to be a restaurant at Ragged Point (north of San Simeon) with beautiful views of the area. Not sure if it's still open.