Sorry to hear about the hdmi cable failure. The 8k the cables are removable and easy to replace.
I do apreciate your situation as with the 4k model the cables are attached to a connector inside the headset. Warrantees are often easier to manage with local retailers (ie Bestbuy) as often they offer to honor some of the manufacturer's warranty but often with a fee and sometimes will offer a better warranty for any issue to replace.
This is often an issue with online retailers like @pinate said with online retailers like Gearbest that doesn't really support the products they sell and often make it a hassle with expenses and run arounds. However it's only been in recent years that some companies like Microsoft & Sony that started covering shipping costs for Mfgr warrantees on things like their consoles or having authorized repair centers. Most still have it in place the consumer pays shipping costs and they effect the repairs due to company size.
Taking the headset apart can be tricky if you don't take time to read up on how to and take the necessary precautions.
@LukeB has linked a video before that details the process; that if mem serves pimax had provided the link for.
Now usually the headset main risk is the intrusion censor that tells the firmware to "brick" if the unit has power when dismantled. Of which just requires the firmware to be reset of which Support has helped users get their headset back up and running. @sjefdeklerk also created a special modified firmware to help users reset as well.
The way to avoid this issue is simply leave the headset unplugged say for 30minutes then with the headset not plugged in try to use the power button to power it on. This will help to disperse any residual power stored in the capacitors.
I will need check but what I would reccommend is replace the hdmi & usb cable with a short cable that ends in a female connector. This way if there is a future cable issue it will be easier to replace. I plan on doing this at sometime in the future.
As I said though this is one of the pitfalls of buying things online is the inconvienence of getting things fixed is always inconvienent on many levels.