I would like to second the recommendation for the Great Escape. It is a large well run dive boat, and they feed you great.
http://www.diveboat.com/
Also, I recommend basing out of the mainland. When you add the cost of the ferry to the Catalina Dive boat chages, the mainland boats are less expensive. You can also board the night before to avoid having to get up earlyin the AM.
Catalina is a great dive spot. I also recomend LaJolla Cove in near by San Diego. It has it all, shore diving, showers, restrooms, kelp, rocks, sand bottom and lots of fish. Easy entry over a short beach, 3 meters into the water and you are diving with tons of fish. You will even see Giant Balck Sea Bass here if you are lucky. Malbu, Palos Verde and Laguna Beach also offer some very good diving.
I also recomend the wetsuit, 7mm or so. Of course you can rent all of your equipment here if you like. Sports Chalet and other dive operators rent the whole rig (wetsuit, tanks, weights) except for the fins, mask and snorkel for $40.00 US. Some dive shops rent the fins and mask too.
If you want to do a couple of shore dives from the mainland, let me know. Of if the kind gentleman who offered to take you on his boat has room, give me a shout.