I used to go to Catalina alot from Dana Point and Oceanside in my 27' Warlock. You willl be fine in your boat. Long Beach Harbor is like 15-20 miles south of L.A. I would suggest going from Long Beach Harbor where it's approx. 26 miles to Catalina. The Catalina ferry goes back and forth on this route, so there is boat traffic and it's safer.
When you get to Catalina, you need a radio to call the Harbor Patrol and they come over and give you a pass to moore your boat (no docks) Then you have to call the water taxi to come drop you off at the main pier to go onto the Island. Sorry, but I don't remember the channels for the Harbor Patrol and Water taxi.
Go to www.catalina.com for alot of info on Catalina Island. I usually stay at the Metropole Hotel. It is very nice. There is some shopping and restaurants and bars there to keep you occupied.
Most of the Island has golf carts for transportation--there are very few cars there. You can rent a golf cart for approx. $90.00 for 3 hours to get around and see the different areas. For the restaurants and bars, you can walk eveywhere.