It's worth getting one and trying, I think your chances of success should be high. It probably already contains some form of microcontroller to read the IR signal and convert it to PWM to drive the LEDs.
You say you want to control it via arduino, will the arduino be in the lamp and be controlled via DMX or do you have some other idea in mind?
Attached is a schematic I did for a RGB mood lamp controlled via an ATtiny85. The LED I used looks the same as yours this may give you an idea of what you may find in the lamp.
ATtiny-RGB Moodlamp.pdf (8.88 KB)