Making my own 38kHz remote
How hard is it to send IR data using a 38KHZ carrier? Pretty easy. Could you easily strip out the internals of a remote and replace it with your own? Probably just as easy. Have a look at the TVBGone code here:

http://learn.adafruit.com/tv-b-gone-kit/download


An ATtiny85 controlling IR LEDs for remote TV control

It turns on/off the PWM generated based on code structures stored in the flash, pretty easy to understand.

See design notes