Yes, the walk up from the car park is fairly long and uphill, but not difficult; quite pleasant in fact.
When I refer to the boulder at the bottom, it's at the bottom of Castle Rock itself where you need to scramble over the boulder and through a gap to access the ladder. Stretching to the few steel handholds anchored in the rocks is the challenging bit. Hopefully they have added some more to make it easier for less flexible people. It is seemingly an unnecessary barrier, given how large, superbly engineered and what a great attraction the Skywalk is. There seems to be no logical reason not to reduce the impediment, for the sake of a few more handholds bolted into the rock.