Mo's experience made me think of how I did this wrong where she did it right. Perhaps you can learn from my mistake.
Only buy original equipment (lamp with the housing included) for your display. A few years ago, I bought a lamp that was the "same" lamp that is used for my display and saved about $150 by purchasing just the lamp and then re-using the housing from the previous lamp. I had no problems installing it and it looked great for the first month or so, but as time wore on, the lamp was frying my light engine because it was producing more heat than the OEM lamp. The light engine had to be replaced and I had to buy a new lamp again.
Others may have had better experience, but I won't purchase another aftermarket lamp. From now on it's OEM only.