Few things to learn really quickly, very much simplified (so no one give me a hard time about the semantics

):
Sashimi: slices of raw seafood
Nigiri: slices of raw seafood, on a "ball" of rice, usually with wasabi in between
Maki: rolls
The green stuff is the "wasabi", very spicy condiment you can use or not use. The pink or white shaved stuff is ginger, and meant to be chewed on between dishes to cleanse the palate (I don't, personally, but DH eats it). If you get a side dish of what looks like wet grass/greens, it's usually a seaweed salad.
Very true...you can love fish and hate sushi. For some it's mental, for others it's texture, others just don't like the taste. I know I only like certain types of sushi while others I don't like. For instance, I love scallops, but do NOT like them raw in sushi. I hate eel/octopus, and definitely still don't like it in sushi

Not a fan of cooked salmon, like it raw in sushi. So there you go, be willing to try anything, it might surprise you.
I agree that for the beginner, california roll is like training wheels. Unless you dislike crab, avocado or cucumber, it's easy peasy. That, and something like a shrimp tempura roll. The only reason I would never order the california roll at California Grill is the ridiculous price they charge for it...I know everything at Disney is humongo upcharge, but that's so far out of line I just can't take it. But considering your situation, for a first time, why not give it a try.
Another thing that might help you pick at CG, if you like rare (or raw) red meat, tuna is easier to transition to raw.
A few tips:
It feels weird to shove a whole roll into your mouth, but (except for those GIGANTIC palm sized ones

) really, it's what you do. Otherwise you tend to end up with it falling apart if you try to bite it in half. Don't worry, the chipmunk cheeks are okay and everyone else has them too.
If you ever have Nigiri anywhere, and wish to dip it into soy sauce, dip it fish side down. Otherwise you lose rice.
It's okay to eat nigiri and roll sushi with your hands (from your own plate, not a shared one). Which is good news for people who struggle with chopsticks. But I know sauces can complicate things, so proceed however you wish
