I've not been to that island, but looking on gmap4, I can follow the Kaupo Trail route from the road passing through Kaupo on the map here.
Using the map, switch between "h - Aerial Google Hybrid" and "t4 - CalTopo Hi-res USA", and zoom in and out to check your route. "t4" zooms out some, but shows the terrain well.
The Aerial Google Hybrid actually labels the "Kaupo Gap Trail Head", which I'd assume is the place to park. Then just follow the 'hybrid' map's trail trace. You can find the topo details on the 't4' map. Interestingly, the t4 map shows a red "cherry stem" park boundary, but it parallels the actual trail shown on both maps.
That has got to be quite a hike: Starts at 1000', and ends at 9800'!! But on this, you could have someone pick you up at the top.
I definitely want to see a trip report if you do it.CalTopo map
is a good one to view, too.