Like many crafts which originated in Japan, their sushi training more or less creates sushi artisans.
If you just want to make a snack, you'll have plenty of ability given a basic review of techniques.
You should focus your learning on understanding food-safety, getting the rice right, and making the roll not fall apart.
The rest is just levels of mastery which you need not approach in your kitchen in order to experiment and enjoy a good dish.
cooking.stackexchange.com/users/1443/Ocaasi
I make sushi with friends about once a month, and it's not too difficult.
The thing that took us the longest to get right was the rice, and we got that down after a few tries.
It'll probably take a while to figure out the amount of vinegar you like in it, and how long to leave the seaweed in it while it's cooking.
For nigiri, I've got a little plexiglass box for molding the rice, which makes it somewhat easier to get it a regular shape.
It probably wouldn't be too hard to find one, if you're really into making nigiri and don't want to just do it by hand.
We also tried making tamago (sweetened omelet) from scratch last time, and it came out really well.
We weren't able to make it the proper thickness and have it cook properly, so we ended up making a bunch of very thin layers, stacking them, then rolling them up and slicing them.
We've started making sunomono as well, which makes a good opening to the meal.
Thinly-sliced cucumber, mackerel, and a little bit of miso dressing cut with some mirin (sweetened rice wine).
Sometimes we throw a little seaweed salad on top, as well.
cooking.stackexchange.com/users/1201/Taeraresh
To be a professional, yes there are schools in Japan that take several years to complete including lengthy apprenticeship requirements.
That said, I've taken a 3 hour sushi class
and I can make sushi rice, maki, nigiri, and hand rolls just fine.
They sometimes lack a little in the appearance department though.
cooking.stackexchange.com/users/60/hobodave
Personally-
I use the sushi rice recipe from "The Joy of Cooking" and it worked on the first try.
You should definitely not be afraid to try it.
It took a couple tries getting the technique right for making the rolls but it's a fun family activity as the children get to pick their fillings, etc.
cooking.stackexchange.com/users/2001/Sobachatina
If you haven't seen it already, check out the sushi documentary Jiro Dreams of Sushi.
He is 86 years old and a national treasure of Japan.
Even he, himself, says he has not mastered sushi.
He dreams all the time of how to improve his techniques.
Hence the name of the movie "Jiro Dreams of Sushi".
I was able to successfully make my own sushi after two attempts.
The hardest thing to grasp is the amount of labor and techniques needed for the rice.
I first had sushi while living in Australia and watched a food tv show about Outback Bush cooking, with a Bushman cook.
I watched him make maki rolls by hand with fish he caught.
After I saw that, I decided I wanted to learn.
It's worthwhile to research how to prepare the rice correctly because 50% of sushi is pure rice.
Good luck!
cooking.stackexchange.com/users/3958/D3vtr0n
I've read somewere in the net that sushi is an extremely difficult food to prepare. It will take at least one year just to learn to cook the rice, and ten year to complete the experience.  It's so difficult? To do a comparison, one could prepare a decent home sushi like one can prepare a decent home dish after some years of home cooking?  It's more like a western chef that needs anyway to study and practice for a long time?
Is sushi so difficult?
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<asian-cuisine><sushi>
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cooking.stackexchange.com/users/1805/pygabriel
A basic review of the techniques should be enough to make sushi without difficulty. The sushi rice recipe from "The Joy of Cooking" is not difficult to master. You can make basic sushi quite easily with just a little practice.
Making basic sushi is quite easy to master and you don't have to be afraid of not mastering all the techniques.