Automatic Engine Swap...

ok ok im extremely new to WRXs so go easy :naughty: ok so say i havea WRX w/ an automatic transmission but in my search for a super sleeper i decide i want to swap out for the STi engine...but decide theres too much traffic in the area to have a stick and not be annoyed. would it be a direct bolt on?
would i need to beef up the transmission?
any other points to this swap and info are greatly appreciated....thank you

Actually I'm pretty sure it would bolt up as long as the final drive ratios matched.