The trip you are considering is a tough one if you only have inshore experience on a small powerboat. If you are a seaman who has taken your powerboat to sea for an extended period, and if you have experience in the sort of storms which you can't run away from, all you need to do is learn how to sail. That is the easy part.
The fact is that everyone who has crossed an ocean had to do it for the first time once. An acquaintance who had sailed a Hatteras 60 sports fishing cruiser for many years made the change to sail. He had been sailing his boat to all the big fishing tournaments in Australia and was a true mariner. He bought a 48 foot sloop to do a circumnavigation of the globe and set out after a season spent learning the ropes and ultimately returned to Darwin after three years with many a tale to tell, but with no problems other than those which would be resolved by any other sailor.
There are a lot of differences between sail power and engine power. The boat behaves differently, doesn't go where you want to go with just a turn of the wheel, and it can't get up and plane away from bad weather. It takes some additional skill to operate a sailboat, but with the addition of a little extra knowledge and a seaworthy yacht, the skill and character which marks you as a seaman will get you across the big blue in a remarkably similar way.
"if at first you don't succeed....Redefine success"!