There's no difference in the test, I'm afraid. If you pass in an automatic, then you're licensed to drive only automatics. You will not be licensed to drive a standard. But it's the exact same test - theory, hazard and practical.
The test is difficult, but it's not unheard of for people to pass without lessons. Still, I'd recommend having a few. If you have lessons with an instructor who uses a manual car, you can take the test in that car -- that way you'd be licensed to drive both manual and automatic. That might be your best bet, unless you have no intention of ever driving a manual.