Is it possible to just buy some replacement fans, ofc I will get the same sized fans, not bigger or smaller and install them on my GPUs? Would that interfere in any way with the card?
Not just possible, it's often better.
You need a good fans (Delta Electronics), same size as heat sink. Not gpu fans, just fans.
Then remove everything from card except the heat sink and put a new ones firmly.
You need an external power supply for it, not from card but from PSU or MB. And it'll be noiser.
In my practice, the cooling is even better than the original solution. It also often cheaper and designed to work 24/7 at 100%, unlike original fans which worn out quite fast if set to 100%.
In case of turbine cooling new heat sink might be needed if it doesn't allow air intake from a top of it.
https://youtu.be/G5KdntuEbLM