PSA to anyone whose DC is having trouble reading games - a defective power board preventing the correct voltage from being distributed throughout the system can give the same symptoms as a dead laser, so your drive might be totally fine... worth checking if there's any bulged caps or something else obviously wrong with the power board when repairing the drive or thinking of replacing parts on the drive.
Just my 2 cents but I have repaired 2 systems that would not start by replacing the entire GD rom assembly. The third system that would not start, I dropped in a GDEMU and never looked back. I did try replacing just the laser once with a new laser and just wasted a few bucks. Never worked.