I love sushi. But I agree, try various rolls because, well, they have less fish than the other things. (I know that doesn't mean a thing to you, but I forget the japanese names for these). Rolls usually come in sets of 6, while the others come in 2 per order.
And dipping them into a wasabi - soy sauce mixture greatly diminishes the fish taste, especially if you have a lot of wasabi (it's quite strong, I warn ya!).
Also, some fish tastes more like fish than others... I think I had mackrel on Sunday, and it had a very STRONG fish flavor. Most don't. Tuna and salmon are good starters.
But the best idea is to go to a sushi place with someone who enjoys it. You order a cooked meal and "steal" sushi off their plate. I recommend you try a couple of theirs before you "damage" your palate with the cooked food. I don't know if it matters, but it can't hurt.