Its easy to get there. Take Highway 80 west, exit onto Highway 89 toward Sierraville. At Sierraville you make a left on highway 49 toward Downiville. Approximatley 20-30 minutes from Sierraville is a small town called Bassetts. Turn right at Bassetts onto Gold Lake Road. A few miles on that road you will see a sign on your left that says "Gold Lake Boat ramp"-turn there. The first right off that road will take you right to the boat launch. You can launch your boat there, leave the trailer and drive back to the campsite or leave your rig/trailer there and take the boat to the camp area.
To get back to the campsites go back the same way you came down to it. This time turn right on the road you came down. It will quickly turn to a dirt road. Hang a left at the "Y" and follow that 4x4 road all the way around to the backside of the lake. You can't miss the campsites there just keep driving until you get to them.
When we were there, there was a full size 20' mastercraft ski boat pulling skiiers all day long. They were camped down the way from us so I don't think there is a boat size restriction. The lake is BIG.
Also there was no launch fee that I saw and I knwo there was no campsite fees.
http://www.mapquest.com/maps?city=Bassetts&state=CA
If you zoom into the red star you will see Gold Lake Road and the lake under the box that has S620 in it is Gold Lake.
I can't wait to go back there.