this is my first day with my new macbook pro (first few hours in fact) and my first mac ever so i was already pretty nervous. the same catastrophe happened to me when i tried to install some new RAM. I installed it badly, not realizing how hard i had to push that guy in there. anyway, the standby light started blinking and the screen was dead. i took the new ram out, no change, still dead. MADDENING.
i did finally get it working again though. Making sure the power was off by holding the power button down for several seconds, I took the original RAM out of it's slot, left that slot empty and then placed it in the other slot and rebooted. Success! I shut down again, then i took that RAM out again put it back in it's original slot and placed the new RAM in the top slot (nice and tight this time). turn back on.
Working and with all the RAM! i can't explain this problem. but this solution worked for me. i hope you have similar luck!