I'm sure there's a million "Sushi for the Uninitiated" guides, but here's my quick take. We're OT licenced here, and I'm using it!
If you've had smoked salmon, also known as "lox", then you're half-way there. That's kind of the beef-jerky of the fish world. It's a 'gateway' food for some, kind of like the french fries at Taco Bell.
Stick to what you know and build out from there. Don't do eel or squid unless you're ready for it. Newbie sushi people usually aren't offended by salmon ("sake") or tuna ("toro" or "maguro"). The taste is familar, but when raw, it's a lot more intense. Good fish is really very smooth, but it takes a good sushi "chef" to find it. As a rule, it would seem the farther inland you go, the harder it is to find really good sushi.
If you're worried about wasabe, which is a green mustard paste with a very strong bite, you'd best stick with sashimi, which is just sliced raw fish. This will come with the wasabe and pickled ginger ("gari") on the side, so you can use it as you see fit. It's just tuna or salmon, so you know what to expect.
As a rule: The stuff you find pre-packaged in plastic containers at the local mall is not sushi. It's to sushi what a hamburger is to a good steak. They might look the same, adhere to the same basic technical definition, but really, you're fooling yourself.
When you get more advanced, you can tackle the more exciting stuff. If you're not sweating, you're not trying hard enough. The wasabe is a mustard, and from what I've found, even those used to spicy food are really burned by some of it. Chile hot and mustard hot are two different things, with mustard acting a lot more in the nose. Especially mustard oil, which I swear, is the sushi "chef"'s secret weapon. Do not taunt the chef, or they might spike your next roll with this stuff. Since it's a clear liquid, you're not going to see it.
Good sushi isn't cheap, but then, neither is good fish. Done right, though, sushi is a lot cheaper than binging on oysters, and it can be a whole lot more fun too.
Take the time to do it right and you'll probably enjoy it.