Can't think of any way to test, other than hooking an oscilloscope up to the legs of the IR transmitter LED.
If you prefer not to open your remote, then I guess a scope across a IR detector (a straight 2 pin diode, not a 3 pin demodulator) might do the job, but you would be looking for very small signals.
My guess would be that 36KHz is correct. Maybe Google a few other sites and see what other sources suggest.
I use a 38KHz receiver for 36, 38 and 40KHz signals without noticable problems.
In theory I may be limiting the range by up to half by being 2KHz out, but it never seems to have mattered to me.