Warranty
4. What kind of activities are excluded from my warranty coverage?
Apples One-Year Limited Warranty for iMac excludes coverage for damage resulting from a number of events, including accident, liquid spill or submersion, unauthorized service and unauthorized modifications. If damage is outside the scope of warranty coverage, service may be available through a local AASP or an Apple retail store, but all service charges will be your responsibility. In such an event, you will be asked to approve the estimated charges and accept the terms and conditions for service before authorizing the repair. If the repair is performed at an Apple retail store Apple's Repair Terms and Conditions will govern service. Repair service for a iMac that has experienced catastrophic damage, for example extensive liquid damage or a severe impact that results in the product being disassembled into multiple pieces, is generally not available and not eligible for service.
This is from the iMac-FAQ......
Where do you get the idea that it voids the warranty? I can't speak for the sock monkey hostel, but in the US you're fine. Unless the later failure was caused by the work you did, your warranty is fine.
Certainly, the easiest way to avoid that potential eventuality is to not do the work yourself in the first place, but if you're competent enough to be doing the work in the first place, you shouldn't be worried about it.
4. What kind of activities are excluded from my warranty coverage?
Apples One-Year Limited Warranty for iMac excludes coverage for damage resulting from a number of events, including accident, liquid spill or submersion, unauthorized service and unauthorized modifications. If damage is outside the scope of warranty coverage, service may be available through a local AASP or an Apple retail store, but all service charges will be your responsibility. In such an event, you will be asked to approve the estimated charges and accept the terms and conditions for service before authorizing the repair. If the repair is performed at an Apple retail store Apple's Repair Terms and Conditions will govern service. Repair service for a iMac that has experienced catastrophic damage, for example extensive liquid damage or a severe impact that results in the product being disassembled into multiple pieces, is generally not available and not eligible for service.
This is from the iMac-FAQ......