Can the pin (that penetrates the k-cup) be replaced?

Askbelieveachieve the top piercing needle is part of an assembly. Not sure if there is a replacement available, but to get to it follow How to open and clean Keurig Coffee Maker|this guide] up to Step 5. There you see two screws that hold the assembly (red)

as well as two smaller screws that hold the water supply line to the water inlet (blue). If you have not already done so, remove the two bottom screws from the assembly

With all screws removed a push on the water inlet spout downwards should free the assembly. That was the fun part. The hard part will be to find a replacement. Every now and then they pop up at places like this