It's not too difficult and is well traveled...
99 to 59 in Merced (curves around in Snelling, then left onto J59/LaGrange Rd)...
Go to Red Hills, then Right onto RedHills Rd and right onto 120 at Chinese Camp.
Another 14 miles to Groveland...where you must pick between Old Priest Grade Rd. or New Priest Grade Rd. (the new one is longer, but has an easier incline).
(Edit) Then, pass the town of Groveland another 18 miles to the "Yosemite Lakes RV Resort."
There are options, but they involve more backroad (hills and curves) driving.
Safe travels