You likely should remove the majority of the perferals that were not with the product at time of purchase - as they may not be returned to you if say, they simply send you a replacement.
Adding ram will likely not void your warranty, as it has pretty much no impact on power surges, which is what seems like what happened to your computer. That or you baked it and some sodering got crossed.
I feel sorry for you friend. I went through similar things around the time of the 1.0 launch, along with a buckload of personal drama at the time. (A synopsis of it is actually published on one of the "I Remember" documentries about 1.xx.) I hope you can get your rig up and running again at full steam soon.
Me, I just installed my new graphics card I bought for my birthday, and am in awe of how pretty the game is in comparison.